[PATCH] D124867: [SLP][NFC] Pre-commit test showing horizontal reduction preventing FMA

[Bill Schmidt via Phabricator via llvm-commits]

wjschmidt updated this revision to Diff 427037.
wjschmidt added a comment.

I've made all requested changes, with the exception that I can't remove the loop structure or any of the undefs without breaking the test.  In both cases, we no longer generate the horizontal reduction.  I've made all the reductions Alexey requested, and changed the variable names as Vasileios requested.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124867/new/

https://reviews.llvm.org/D124867

Files:
  llvm/test/Transforms/SLPVectorizer/X86/slp-reduc-fma-loss.ll


Index: llvm/test/Transforms/SLPVectorizer/X86/slp-reduc-fma-loss.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SLPVectorizer/X86/slp-reduc-fma-loss.ll
@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -slp-vectorizer -S -mcpu=core-avx2 -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+; This test checks for a case when a horizontal reduction of floating-point
+; adds may look profitable, but is not because it eliminates generation of
+; floating-point FMAs that would be more profitable.
+; FIXME: We currently generate the horizontal reduction.
+
+define void @foo() #0 {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[PHI0:%.*]] = phi double [ 0.000000e+00, [[TMP0:%.*]] ], [ [[OP_RDX:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[CVT0:%.*]] = uitofp i16 undef to double
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <4 x double> poison, double [[CVT0]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = fmul fast <4 x double> poison, [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = call fast double @llvm.vector.reduce.fadd.v4f64(double -0.000000e+00, <4 x double> [[TMP2]])
+; CHECK-NEXT:    [[OP_RDX]] = fadd fast double [[TMP3]], [[PHI0]]
+; CHECK-NEXT:    br i1 undef, label [[EXIT:%.*]], label [[LOOP]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+  br label %loop
+
+loop:
+  %phi0 = phi double [ 0.000000e+00, %0 ], [ %add3, %loop ]
+  %cvt0 = uitofp i16 undef to double
+  %mul0 = fmul fast double undef, %cvt0
+  %add0 = fadd fast double %mul0, %phi0
+  %mul1 = fmul fast double undef, undef
+  %add1 = fadd fast double %mul1, %add0
+  %mul2 = fmul fast double undef, undef
+  %add2 = fadd fast double %mul2, %add1
+  %mul3 = fmul fast double undef, undef
+  %add3 = fadd fast double %mul3, %add2
+  br i1 undef, label %exit, label %loop
+
+exit:
+  ret void
+}


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