cd1e6a587b
Its expected that the sequence `return X > 0.0 ? X : -X`, compiled with -Ofast, produces fabs intrinsic. However, at this point, LLVM is unable to do so. The above sequence goes through the following transformation during the pass pipeline: 1) SROA pass generates the phi node. Here, it does not infer the fast-math flags on the phi node unlike clang frontend typically does. 2) Phi node eventually gets translated into select instruction. Because of missing no-signed-zeros(nsz) fast-math flag on the select instruction, InstCombine pass fails to fold the sequence into fabs intrinsic. This patch, as a part of SROA, tries to propagate nsz fast-math flag on the phi node using function attribute enabling this folding. Closes #51601 Co-authored-by: Sushant Gokhale <sgokhale@nvidia.com>
80 lines
3.0 KiB
LLVM
80 lines
3.0 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
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; RUN: opt < %s -passes='sroa' -S | FileCheck %s
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define double @phi_with_nsz(double %x) "no-signed-zeros-fp-math"="true" {
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; CHECK-LABEL: define double @phi_with_nsz(
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; CHECK-SAME: double [[X:%.*]]) #[[ATTR0:[0-9]+]] {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[CMP:%.*]] = fcmp olt double [[X]], 0.000000e+00
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; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: [[FNEG:%.*]] = fneg double [[X]]
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; CHECK-NEXT: br label [[RETURN]]
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; CHECK: return:
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; CHECK-NEXT: [[X_ADDR_0:%.*]] = phi nsz double [ [[FNEG]], [[IF_THEN]] ], [ undef, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret double [[X_ADDR_0]]
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entry:
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%x.addr = alloca double
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%cmp = fcmp olt double %x, 0.0
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br i1 %cmp, label %if.then, label %return
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if.then: ; preds = %entry
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%fneg = fneg double %x
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store double %fneg, ptr %x.addr
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br label %return
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return: ; preds = %entry,%if.then
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%retval = load double, ptr %x.addr
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ret double %retval
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}
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define <2 x double> @vector_phi_with_nsz(<2 x double> %x, i1 %cmp, <2 x double> %a, <2 x double> %b) "no-signed-zeros-fp-math"="true" {
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; CHECK-LABEL: define <2 x double> @vector_phi_with_nsz(
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; CHECK-SAME: <2 x double> [[X:%.*]], i1 [[CMP:%.*]], <2 x double> [[A:%.*]], <2 x double> [[B:%.*]]) #[[ATTR0]] {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: br label [[RETURN]]
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; CHECK: return:
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; CHECK-NEXT: [[X_ADDR_0:%.*]] = phi nsz <2 x double> [ [[B]], [[IF_THEN]] ], [ [[A]], [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret <2 x double> [[X_ADDR_0]]
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entry:
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%x.addr = alloca <2 x double>
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store <2 x double> %a, ptr %x.addr
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br i1 %cmp, label %if.then, label %return
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if.then: ; preds = %entry
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store <2 x double> %b, ptr %x.addr
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br label %return
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return: ; preds = %entry,%if.then
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%retval = load <2 x double>, ptr %x.addr
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ret <2 x double> %retval
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}
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define double @phi_without_nsz(double %x) "no-signed-zeros-fp-math"="false" {
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; CHECK-LABEL: define double @phi_without_nsz(
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; CHECK-SAME: double [[X:%.*]]) #[[ATTR1:[0-9]+]] {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[CMP:%.*]] = fcmp olt double [[X]], 0.000000e+00
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; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: [[FNEG:%.*]] = fneg double [[X]]
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; CHECK-NEXT: br label [[RETURN]]
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; CHECK: return:
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; CHECK-NEXT: [[X_ADDR_0:%.*]] = phi double [ [[FNEG]], [[IF_THEN]] ], [ undef, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret double [[X_ADDR_0]]
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entry:
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%x.addr = alloca double
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%cmp = fcmp olt double %x, 0.0
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br i1 %cmp, label %if.then, label %return
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if.then: ; preds = %entry
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%fneg = fneg double %x
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store double %fneg, ptr %x.addr
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br label %return
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return: ; preds = %entry,%if.then
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%retval = load double, ptr %x.addr
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ret double %retval
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}
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