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dace98d805
The loop rerolling pass was failing with an assertion failure from a
failed cast on loops like this:
void foo(int *A, int *B, int m, int n) {
for (int i = m; i < n; i+=4) {
A[i+0] = B[i+0] * 4;
A[i+1] = B[i+1] * 4;
A[i+2] = B[i+2] * 4;
A[i+3] = B[i+3] * 4;
}
}
The code was casting the SCEV-expanded code for the new
induction variable to a phi-node. When the loop had a non-constant
lower bound, the SCEV expander would end the code expansion with an
add insted of a phi node and the cast would fail.
It looks like the cast to a phi node was only needed to get the
induction variable value coming from the backedge to compute the end
of loop condition. This patch changes the loop reroller to compare
the induction variable to the number of times the backedge is taken
instead of the iteration count of the loop. In other words, we stop
the loop when the current value of the induction variable ==
IterationCount-1. Previously, the comparison was comparing the
induction variable value from the next iteration == IterationCount.
This problem only seems to occur on 32-bit targets. For some reason,
the loop is not rerolled on 64-bit targets.
PR18290
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198425 91177308-0d34-0410-b5e6-96231b3b80d8
97 lines
3.5 KiB
LLVM
97 lines
3.5 KiB
LLVM
; RUN: opt < %s -loop-reroll -S | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define i32 @foo(i32* nocapture readonly %x) #0 {
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%r.029 = phi i32 [ 0, %entry ], [ %add12, %for.body ]
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%arrayidx = getelementptr inbounds i32* %x, i64 %indvars.iv
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%0 = load i32* %arrayidx, align 4
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%add = add nsw i32 %0, %r.029
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%1 = or i64 %indvars.iv, 1
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%arrayidx3 = getelementptr inbounds i32* %x, i64 %1
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%2 = load i32* %arrayidx3, align 4
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%add4 = add nsw i32 %add, %2
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%3 = or i64 %indvars.iv, 2
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%arrayidx7 = getelementptr inbounds i32* %x, i64 %3
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%4 = load i32* %arrayidx7, align 4
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%add8 = add nsw i32 %add4, %4
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%5 = or i64 %indvars.iv, 3
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%arrayidx11 = getelementptr inbounds i32* %x, i64 %5
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%6 = load i32* %arrayidx11, align 4
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%add12 = add nsw i32 %add8, %6
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 4
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%7 = trunc i64 %indvars.iv.next to i32
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%cmp = icmp slt i32 %7, 400
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br i1 %cmp, label %for.body, label %for.end
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; CHECK-LABEL: @foo
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; CHECK: for.body:
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; CHECK: %indvar = phi i64 [ %indvar.next, %for.body ], [ 0, %entry ]
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; CHECK: %r.029 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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; CHECK: %arrayidx = getelementptr inbounds i32* %x, i64 %indvar
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; CHECK: %0 = load i32* %arrayidx, align 4
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; CHECK: %add = add nsw i32 %0, %r.029
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; CHECK: %indvar.next = add i64 %indvar, 1
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; CHECK: %exitcond = icmp eq i64 %indvar, 399
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; CHECK: br i1 %exitcond, label %for.end, label %for.body
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; CHECK: ret
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for.end: ; preds = %for.body
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ret i32 %add12
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}
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define float @bar(float* nocapture readonly %x) #0 {
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
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%r.029 = phi float [ 0.0, %entry ], [ %add12, %for.body ]
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%arrayidx = getelementptr inbounds float* %x, i64 %indvars.iv
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%0 = load float* %arrayidx, align 4
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%add = fadd float %0, %r.029
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%1 = or i64 %indvars.iv, 1
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%arrayidx3 = getelementptr inbounds float* %x, i64 %1
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%2 = load float* %arrayidx3, align 4
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%add4 = fadd float %add, %2
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%3 = or i64 %indvars.iv, 2
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%arrayidx7 = getelementptr inbounds float* %x, i64 %3
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%4 = load float* %arrayidx7, align 4
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%add8 = fadd float %add4, %4
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%5 = or i64 %indvars.iv, 3
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%arrayidx11 = getelementptr inbounds float* %x, i64 %5
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%6 = load float* %arrayidx11, align 4
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%add12 = fadd float %add8, %6
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 4
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%7 = trunc i64 %indvars.iv.next to i32
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%cmp = icmp slt i32 %7, 400
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br i1 %cmp, label %for.body, label %for.end
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; CHECK-LABEL: @bar
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; CHECK: for.body:
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; CHECK: %indvar = phi i64 [ %indvar.next, %for.body ], [ 0, %entry ]
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; CHECK: %r.029 = phi float [ 0.000000e+00, %entry ], [ %add, %for.body ]
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; CHECK: %arrayidx = getelementptr inbounds float* %x, i64 %indvar
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; CHECK: %0 = load float* %arrayidx, align 4
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; CHECK: %add = fadd float %0, %r.029
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; CHECK: %indvar.next = add i64 %indvar, 1
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; CHECK: %exitcond = icmp eq i64 %indvar, 399
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; CHECK: br i1 %exitcond, label %for.end, label %for.body
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; CHECK: ret
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for.end: ; preds = %for.body
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ret float %add12
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}
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attributes #0 = { nounwind readonly uwtable }
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