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[InstCombine] Extend saturating idempotent atomicrmw transform to FP 

I'm assuming that the nan propogation logic for InstructonSimplify's handling of fadd and fsub is correct, and applying the same to atomicrmw.

Differential Revision: https://reviews.llvm.org/D58836

llvm-svn: 355222
This commit is contained in:
Philip Reames 2019-03-01 19:50:36 +00:00
parent 6e1e7e1c3e
commit cf0a978e1f
2 changed files with 13 additions and 5 deletions
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12
llvm/lib/Transforms/InstCombine/InstCombineAtomicRMW.cpp
View File

@ -57,15 +57,23 @@ bool isIdempotentRMW(AtomicRMWInst& RMWI) {
}
/// Return true if the given instruction always produces a value in memory
/// equivelent to its value operand.
/// equivalent to its value operand.
bool isSaturating(AtomicRMWInst& RMWI) {
if (auto CF = dyn_cast<ConstantFP>(RMWI.getValOperand()))
switch(RMWI.getOperation()) {
case AtomicRMWInst::FAdd:
case AtomicRMWInst::FSub:
return CF->isNaN();
default:
return false;
};
auto C = dyn_cast<ConstantInt>(RMWI.getValOperand());
if(!C)
return false;
switch(RMWI.getOperation()) {
default:
// TODO: fadd, fsub w/Nan
return false;
case AtomicRMWInst::Xchg:
return true;

6
llvm/test/Transforms/InstCombine/atomicrmw.ll
View File

@ -214,7 +214,7 @@ define i8 @sat_max_smax_char(i8* %addr) {
}
; CHECK-LABEL: sat_fadd_nan
; CHECK-NEXT: %res = atomicrmw fadd double* %addr, double 0x7FF00000FFFFFFFF release
; CHECK-NEXT: %res = atomicrmw xchg double* %addr, double 0x7FF00000FFFFFFFF release
; CHECK-NEXT: ret double %res
define double @sat_fadd_nan(double* %addr) {
%res = atomicrmw fadd double* %addr, double 0x7FF00000FFFFFFFF release
@ -222,7 +222,7 @@ define double @sat_fadd_nan(double* %addr) {
}
; CHECK-LABEL: sat_fsub_nan
; CHECK-NEXT: %res = atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF release
; CHECK-NEXT: %res = atomicrmw xchg double* %addr, double 0x7FF00000FFFFFFFF release
; CHECK-NEXT: ret double %res
define double @sat_fsub_nan(double* %addr) {
%res = atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF release
@ -230,7 +230,7 @@ define double @sat_fsub_nan(double* %addr) {
}
; CHECK-LABEL: sat_fsub_nan_unused
; CHECK-NEXT: atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF monotonic
; CHECK-NEXT: store atomic double 0x7FF00000FFFFFFFF, double* %addr monotonic, align 8
; CHECK-NEXT: ret void
define void @sat_fsub_nan_unused(double* %addr) {
atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF monotonic