[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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351010 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index ac989dd..b44fe5a 100644
--- a/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -714,10 +714,30 @@
!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;
}
diff --git a/test/Transforms/LoopVectorize/libcall-remark.ll b/test/Transforms/LoopVectorize/libcall-remark.ll
new file mode 100644
index 0000000..a1a7e46
--- /dev/null
+++ b/test/Transforms/LoopVectorize/libcall-remark.ll
@@ -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)
+
