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Fixed the lost FastMathFlags in GVN(Global Value Numbering). 

Reviewer: Hal Finkel.
Differential Revision: https://reviews.llvm.org/D26952

llvm-svn: 287700
This commit is contained in:
Vyacheslav Klochkov 2016-11-22 20:52:53 +00:00
parent f4de3b68bb
commit 9a630dfb57
2 changed files with 35 additions and 1 deletions
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7
llvm/lib/Transforms/Scalar/GVN.cpp
View File

@ -1731,7 +1731,12 @@ static void patchReplacementInstruction(Instruction *I, Value *Repl) {
// Patch the replacement so that it is not more restrictive than the value
// being replaced.
ReplInst->andIRFlags(I);
// Note that if 'I' is a load being replaced by some operation,
// for example, by an arithmetic operation, then andIRFlags()
// would just erase all math flags from the original arithmetic
// operation, which is clearly not wanted and not needed.
if (!isa<LoadInst>(I))
ReplInst->andIRFlags(I);
// FIXME: If both the original and replacement value are part of the
// same control-flow region (meaning that the execution of one

29
llvm/test/Transforms/GVN/propagate-ir-flags.ll Normal file
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@ -0,0 +1,29 @@
; RUN: opt < %s -gvn -S | FileCheck %s
; CHECK-LABEL: func_fast
; CHECK: fadd fast double
; CHECK-NEXT: store
; CHECK-NEXT: ret
define double @func_fast(double %a, double %b) {
entry:
%a.addr = alloca double, align 8
%add = fadd fast double %b, 3.000000e+00
store double %add, double* %a.addr, align 8
%load_add = load double, double* %a.addr, align 8
ret double %load_add
}
; CHECK-LABEL: func_no_fast
; CHECK: fadd double
; CHECK-NEXT: store
; CHECK-NEXT: ret
define double @func_no_fast(double %a, double %b) {
entry:
%a.addr = alloca double, align 8
%add = fadd fast double %b, 3.000000e+00
store double %add, double* %a.addr, align 8
%duplicated_add = fadd double %b, 3.000000e+00
ret double %duplicated_add
}