llvm/test/Transforms/InstCombine/no_cgscc_assert.ll
Sanjay Patel 2234dddb07 [LibCallSimplifier] use instruction-level fast-math-flags to transform sqrt calls
This is a continuation of adding FMF to call instructions:
http://reviews.llvm.org/rL255555

The intent of the patch is to preserve the current behavior of the transform except
that we use the sqrt instruction's 'fast' attribute as a trigger rather than the
function-level attribute.

But this raises a bug noted by the new FIXME comment.

In order to do this transform:
sqrt((x * x) * y) ---> fabs(x) * sqrt(y)

...we need all of the sqrt, the first fmul, and the second fmul to be 'fast'. 
If any of those ops is strict, we should bail out.

Differential Revision: http://reviews.llvm.org/D15937



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257400 91177308-0d34-0410-b5e6-96231b3b80d8
2016-01-11 22:34:19 +00:00

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LLVM

; RUN: opt < %s -inline -instcombine -S | FileCheck %s
; PR21403: http://llvm.org/bugs/show_bug.cgi?id=21403
; When the call to sqrtf is replaced by an intrinsic call to fabs,
; it should not cause a problem in CGSCC.
define float @bar(float %f) #0 {
%mul = fmul fast float %f, %f
%call1 = call fast float @sqrtf(float %mul)
ret float %call1
; CHECK-LABEL: @bar(
; CHECK-NEXT: call fast float @llvm.fabs.f32
; CHECK-NEXT: ret float
}
declare float @sqrtf(float)