mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-07-21 18:29:45 +00:00
10bb82e54f
Patch by Michele Scandale! Rewrite of the functions used to compute the backedge taken count of a loop on LT and GT comparisons. I decided to split the handling of LT and GT cases becasue the trick "a > b == -a < -b" in some cases prevents the trip count computation due to the multiplication by -1 on the two operands of the comparison. This issue comes from the conservative computation of value range of SCEVs: taking the negative SCEV of an expression that have a small positive range (e.g. [0,31]), we would have a SCEV with a fullset as value range. Indeed, in the new rewritten function I tried to better handle the maximum backedge taken count computation when MAX/MIN expression are used to handle the cases where no entry guard is found. Some test have been modified in order to check the new value correctly (I manually check them and reasoning on possible overflow the new values seem correct). I finally added a new test case related to the multiplication by -1 issue on GT comparisons. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194116 91177308-0d34-0410-b5e6-96231b3b80d8
416 lines
12 KiB
LLVM
416 lines
12 KiB
LLVM
; RUN: opt -analyze -scalar-evolution -S < %s | FileCheck %s
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; Every combination of
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; - starting at 0, 1, or %x
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; - steping by 1 or 2
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; - stopping at %n or %n*2
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; - using nsw, or not
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; Some of these represent missed opportunities.
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; CHECK: Determining loop execution counts for: @foo
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; CHECK: Loop %loop: backedge-taken count is (-1 + %n)
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; CHECK: Loop %loop: max backedge-taken count is 6
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define void @foo(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @step2
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; CHECK: Loop %loop: Unpredictable backedge-taken count.
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; CHECK: Loop %loop: Unpredictable max backedge-taken count.
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define void @step2(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @start1
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; CHECK: Loop %loop: backedge-taken count is (-2 + (2 smax %n))
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; CHECK: Loop %loop: max backedge-taken count is 5
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define void @start1(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @start1_step2
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; CHECK: Loop %loop: Unpredictable backedge-taken count.
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; CHECK: Loop %loop: Unpredictable max backedge-taken count.
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define void @start1_step2(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @startx
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; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax %n))
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; CHECK: Loop %loop: max backedge-taken count is -1
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define void @startx(i4 %n, i4 %x) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @startx_step2
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; CHECK: Loop %loop: Unpredictable backedge-taken count.
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; CHECK: Loop %loop: Unpredictable max backedge-taken count.
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define void @startx_step2(i4 %n, i4 %x) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @nsw
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; CHECK: Loop %loop: backedge-taken count is (-1 + %n)
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; CHECK: Loop %loop: max backedge-taken count is 6
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define void @nsw(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; If %n is INT4_MAX, %i.next will wrap. The nsw bit says that the
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; result is undefined. Therefore, after the loop's second iteration,
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; we are free to assume that the loop exits. This is valid because:
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; (a) %i.next is a poison value after the second iteration, which can
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; also be considered an undef value.
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; (b) the return instruction enacts a side effect that is control
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; dependent on the poison value.
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;
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; CHECK-LABEL: nsw_step2
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; CHECK: Determining loop execution counts for: @nsw_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + %n) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @nsw_step2(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK-LABEL: nsw_start1
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; CHECK: Determining loop execution counts for: @nsw_start1
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; CHECK: Loop %loop: backedge-taken count is (-2 + (2 smax %n))
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; CHECK: Loop %loop: max backedge-taken count is 5
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define void @nsw_start1(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @nsw_start1_step2
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; CHECK: Loop %loop: backedge-taken count is ((-2 + (3 smax %n)) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @nsw_start1_step2(i4 %n) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @nsw_startx
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; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax %n))
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; CHECK: Loop %loop: max backedge-taken count is -1
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define void @nsw_startx(i4 %n, i4 %x) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @nsw_startx_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax %n)) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 7
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define void @nsw_startx_step2(i4 %n, i4 %x) {
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entry:
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%s = icmp sgt i4 %n, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %n
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even
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; CHECK: Loop %loop: backedge-taken count is (-1 + (2 * %n))
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; CHECK: Loop %loop: max backedge-taken count is 5
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define void @even(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + (2 * %n)) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @even_step2(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_start1
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; CHECK: Loop %loop: backedge-taken count is (-2 + (2 smax (2 * %n)))
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; CHECK: Loop %loop: max backedge-taken count is 4
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define void @even_start1(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_start1_step2
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; CHECK: Loop %loop: backedge-taken count is ((-2 + (3 smax (2 * %n))) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @even_start1_step2(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_startx
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; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax (2 * %n)))
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; CHECK: Loop %loop: max backedge-taken count is -2
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define void @even_startx(i4 %n, i4 %x) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_startx_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax (2 * %n))) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 7
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define void @even_startx_step2(i4 %n, i4 %x) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw
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; CHECK: Loop %loop: backedge-taken count is (-1 + (2 * %n))
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; CHECK: Loop %loop: max backedge-taken count is 5
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define void @even_nsw(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + (2 * %n)) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @even_nsw_step2(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 0, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw_start1
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; CHECK: Loop %loop: backedge-taken count is (-2 + (2 smax (2 * %n)))
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; CHECK: Loop %loop: max backedge-taken count is 4
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define void @even_nsw_start1(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw_start1_step2
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; CHECK: Loop %loop: backedge-taken count is ((-2 + (3 smax (2 * %n))) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 2
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define void @even_nsw_start1_step2(i4 %n) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ 1, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw_startx
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; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax (2 * %n)))
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; CHECK: Loop %loop: max backedge-taken count is -2
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define void @even_nsw_startx(i4 %n, i4 %x) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 1
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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; CHECK: Determining loop execution counts for: @even_nsw_startx_step2
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; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax (2 * %n))) /u 2)
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; CHECK: Loop %loop: max backedge-taken count is 7
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define void @even_nsw_startx_step2(i4 %n, i4 %x) {
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entry:
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%m = shl i4 %n, 1
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%s = icmp sgt i4 %m, 0
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br i1 %s, label %loop, label %exit
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loop:
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%i = phi i4 [ %x, %entry ], [ %i.next, %loop ]
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%i.next = add nsw i4 %i, 2
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%t = icmp slt i4 %i.next, %m
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br i1 %t, label %loop, label %exit
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exit:
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ret void
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}
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