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LoopVectorize: Vectorize all accesses in address space zero with unit stride

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We can vectorize them because in the case where we wrap in the address space the
unvectorized code would have had to access a pointer value of zero which is
undefined behavior in address space zero according to the LLVM IR semantics.
(Thank you Duncan, for pointing this out to me).

Fixes PR16592.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186088 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer
2013-07-11 15:21:55 +00:00
parent 12fa02841c
commit 11eb51e239
2 changed files with 77 additions and 8 deletions
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test/Transforms/LoopVectorize/safegep.ll
+61
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; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-unroll=1 < %s | FileCheck %s
target datalayout = "e-p:32:32:32-S128-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f16:16:16-f32:32:32-f64:32:64-f128:128:128-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
; We can vectorize this code because if the address computation would wrap then
; a load from 0 would take place which is undefined behaviour in address space 0
; according to LLVM IR semantics.
; PR16592
; CHECK: safe
; CHECK: <4 x float>
define void @safe(float* %A, float* %B, float %K) {
entry:
br label %"<bb 3>"
"<bb 3>":
%i_15 = phi i32 [ 0, %entry ], [ %i_19, %"<bb 3>" ]
%pp3 = getelementptr float* %A, i32 %i_15
%D.1396_10 = load float* %pp3, align 4
%pp24 = getelementptr float* %B, i32 %i_15
%D.1398_15 = load float* %pp24, align 4
%D.1399_17 = fadd float %D.1398_15, %K
%D.1400_18 = fmul float %D.1396_10, %D.1399_17
store float %D.1400_18, float* %pp3, align 4
%i_19 = add nsw i32 %i_15, 1
%exitcond = icmp ne i32 %i_19, 64
br i1 %exitcond, label %"<bb 3>", label %return
return:
ret void
}
; In a non-default address space we don't have this rule.
; CHECK: notsafe
; CHECK-NOT: <4 x float>
define void @notsafe(float addrspace(5) * %A, float* %B, float %K) {
entry:
br label %"<bb 3>"
"<bb 3>":
%i_15 = phi i32 [ 0, %entry ], [ %i_19, %"<bb 3>" ]
%pp3 = getelementptr float addrspace(5) * %A, i32 %i_15
%D.1396_10 = load float addrspace(5) * %pp3, align 4
%pp24 = getelementptr float* %B, i32 %i_15
%D.1398_15 = load float* %pp24, align 4
%D.1399_17 = fadd float %D.1398_15, %K
%D.1400_18 = fmul float %D.1396_10, %D.1399_17
store float %D.1400_18, float addrspace(5) * %pp3, align 4
%i_19 = add nsw i32 %i_15, 1
%exitcond = icmp ne i32 %i_19, 64
br i1 %exitcond, label %"<bb 3>", label %return
return:
ret void
}