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Reapply r237453 with a fix for the test timeouts.

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The test timeouts were due to instcombine fighting itself. Regression test added.
Original log message:

Canonicalize min/max expressions correctly.

This patch introduces a canonical form for min/max idioms where one operand
is extended or truncated. This often happens when the other operand is a
constant. For example:

  %1 = icmp slt i32 %a, i32 0
    %2 = sext i32 %a to i64
      %3 = select i1 %1, i64 %2, i64 0

Would now be canonicalized into:

  %1 = icmp slt i32 %a, i32 0
    %2 = select i1 %1, i32 %a, i32 0
      %3 = sext i32 %2 to i64

This builds upon a patch posted by David Majenemer
(https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
passively stopped instcombine from ruining canonical patterns. This
patch additionally actively makes instcombine canonicalize too.

Canonicalization of expressions involving a change in type from int->fp
or fp->int are not yet implemented.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237520 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy
2015-05-16 13:10:45 +00:00
parent f01f1c413a
commit bc71c2fd8e
5 changed files with 140 additions and 7 deletions
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84
test/Transforms/InstCombine/minmax-fold.ll Normal file
View File

@@ -0,0 +1,84 @@
; RUN: opt -S -instcombine < %s | FileCheck %s
; CHECK-LABEL: @t1
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sext
define i64 @t1(i32 %a) {
; This is the canonical form for a type-changing min/max.
%1 = icmp slt i32 %a, 5
%2 = select i1 %1, i32 %a, i32 5
%3 = sext i32 %2 to i64
ret i64 %3
}
; CHECK-LABEL: @t2
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sext
define i64 @t2(i32 %a) {
; Check this is converted into canonical form, as above.
%1 = icmp slt i32 %a, 5
%2 = sext i32 %a to i64
%3 = select i1 %1, i64 %2, i64 5
ret i64 %3
}
; CHECK-LABEL: @t3
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: zext
define i64 @t3(i32 %a) {
; Same as @t2, with flipped operands and zext instead of sext.
%1 = icmp ult i32 %a, 5
%2 = zext i32 %a to i64
%3 = select i1 %1, i64 5, i64 %2
ret i64 %3
}
; CHECK-LABEL: @t4
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: trunc
define i32 @t4(i64 %a) {
; Same again, with trunc.
%1 = icmp slt i64 %a, 5
%2 = trunc i64 %a to i32
%3 = select i1 %1, i32 %2, i32 5
ret i32 %3
}
; CHECK-LABEL: @t5
; CHECK-NEXT: icmp
; CHECK-NEXT: zext
; CHECK-NEXT: select
define i64 @t5(i32 %a) {
; Same as @t3, but with mismatched signedness between icmp and zext.
; InstCombine should leave this alone.
%1 = icmp slt i32 %a, 5
%2 = zext i32 %a to i64
%3 = select i1 %1, i64 5, i64 %2
ret i64 %3
}
; CHECK-LABEL: @t6
; CHECK-NEXT: icmp
; CHECK-NEXT: select
; CHECK-NEXT: sitofp
define float @t6(i32 %a) {
%1 = icmp slt i32 %a, 0
%2 = select i1 %1, i32 %a, i32 0
%3 = sitofp i32 %2 to float
ret float %3
}
; CHECK-LABEL: @t7
; CHECK-NEXT: icmp
; CHECK-NEXT: trunc
; CHECK-NEXT: select
define i16 @t7(i32 %a) {
%1 = icmp slt i32 %a, -32768
%2 = trunc i32 %a to i16
%3 = select i1 %1, i16 %2, i16 -32768
ret i16 %3
}