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[LoopVectorizer] give more advice in remark about failure to vectorize call 

Something like this is requested by:
https://bugs.llvm.org/show_bug.cgi?id=40265
...and it seems like a common enough case that we should acknowledge it.

Differential Revision: https://reviews.llvm.org/D56551

llvm-svn: 351010
This commit is contained in:
Sanjay Patel 2019-01-12 15:27:15 +00:00
parent 1b4a240bfe
commit 7d65fe5cd5
2 changed files with 75 additions and 3 deletions
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26
llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
View File

@ -714,10 +714,30 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
!isa<DbgInfoIntrinsic>(CI) &&
!(CI->getCalledFunction() && TLI &&
TLI->isFunctionVectorizable(CI->getCalledFunction()->getName()))) {
ORE->emit(createMissedAnalysis("CantVectorizeCall", CI)
<< "call instruction cannot be vectorized");
// If the call is a recognized math libary call, it is likely that
// we can vectorize it given loosened floating-point constraints.
LibFunc Func;
bool IsMathLibCall =
TLI && CI->getCalledFunction() &&
CI->getType()->isFloatingPointTy() &&
TLI->getLibFunc(CI->getCalledFunction()->getName(), Func) &&
TLI->hasOptimizedCodeGen(Func);
if (IsMathLibCall) {
// TODO: Ideally, we should not use clang-specific language here,
// but it's hard to provide meaningful yet generic advice.
// Also, should this be guarded by allowExtraAnalysis() and/or be part
// of the returned info from isFunctionVectorizable()?
ORE->emit(createMissedAnalysis("CantVectorizeLibcall", CI)
<< "library call cannot be vectorized. "
"Try compiling with -fno-math-errno, -ffast-math, "
"or similar flags");
} else {
ORE->emit(createMissedAnalysis("CantVectorizeCall", CI)
<< "call instruction cannot be vectorized");
}
LLVM_DEBUG(
dbgs() << "LV: Found a non-intrinsic, non-libfunc callsite.\n");
dbgs() << "LV: Found a non-intrinsic callsite.\n");
return false;
}

52
llvm/test/Transforms/LoopVectorize/libcall-remark.ll Normal file
View File

@ -0,0 +1,52 @@
; RUN: opt -S -loop-vectorize < %s 2>&1 -pass-remarks-analysis=.* | FileCheck %s
; Test the optimization remark emitter for recognition
; of a mathlib function vs. an arbitrary function.
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.14.0"
@data = external local_unnamed_addr global [32768 x float], align 16
; CHECK: loop not vectorized: library call cannot be vectorized
define void @libcall_blocks_vectorization() {
entry:
br label %for.body
for.cond.cleanup:
ret void
for.body:
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
%arrayidx = getelementptr inbounds [32768 x float], [32768 x float]* @data, i64 0, i64 %indvars.iv
%t0 = load float, float* %arrayidx, align 4
%sqrtf = tail call float @sqrtf(float %t0)
store float %sqrtf, float* %arrayidx, align 4
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 32768
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
; CHECK: loop not vectorized: call instruction cannot be vectorized
define void @arbitrary_call_blocks_vectorization() {
entry:
br label %for.body
for.cond.cleanup:
ret void
for.body:
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
%arrayidx = getelementptr inbounds [32768 x float], [32768 x float]* @data, i64 0, i64 %indvars.iv
%t0 = load float, float* %arrayidx, align 4
%sqrtf = tail call float @arbitrary(float %t0)
store float %sqrtf, float* %arrayidx, align 4
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 32768
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
declare float @sqrtf(float)
declare float @arbitrary(float)