03de1cb715
InstCombine tries to swap compare operands to match sub instructions
in order to expose "CSE opportunities". However, it doesn't really
make sense to perform this transform in the middle-end, as we cannot
actually CSE the instructions there.
The backend already performs this fold in
18f5446a45/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp (L4236)
on the SDAG level, however this only works within a single basic block.
To handle cross-BB cases, we do need to handle this in the IR layer.
This patch moves the fold from InstCombine to CGP in the backend,
while keeping the same (somewhat dubious) heuristic.
Differential Revision: https://reviews.llvm.org/D152541
156 lines
3.7 KiB
LLVM
156 lines
3.7 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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; Fold
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; (%x - %y) u> %x
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; to
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; @llvm.sub.with.overflow(%x, %y) + extractvalue
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define i1 @t0_basic(i8 %x, i8 %y) {
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; CHECK-LABEL: @t0_basic(
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; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[Y:%.*]], [[X:%.*]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp ugt i8 %t0, %x
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ret i1 %r
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}
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define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
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; CHECK-LABEL: @t1_vec(
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; CHECK-NEXT: [[R:%.*]] = icmp ugt <2 x i8> [[Y:%.*]], [[X:%.*]]
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; CHECK-NEXT: ret <2 x i1> [[R]]
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;
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%t0 = sub <2 x i8> %x, %y
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%r = icmp ugt <2 x i8> %t0, %x
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ret <2 x i1> %r
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}
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; Commutativity
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define i1 @t2_commutative(i8 %x, i8 %y) {
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; CHECK-LABEL: @t2_commutative(
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; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[Y:%.*]], [[X:%.*]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp ult i8 %x, %t0 ; swapped
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ret i1 %r
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}
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; Extra-use tests
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declare void @use8(i8)
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define i1 @t3_extrause0(i8 %x, i8 %y) {
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; CHECK-LABEL: @t3_extrause0(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: call void @use8(i8 [[T0]])
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; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[Y]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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call void @use8(i8 %t0)
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%r = icmp ugt i8 %t0, %x
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ret i1 %r
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}
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; Negative tests
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define i1 @n4_not_commutative(i8 %x, i8 %y) {
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; CHECK-LABEL: @n4_not_commutative(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[T0]], [[Y]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp ugt i8 %t0, %y ; can't check against %y.
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ret i1 %r
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}
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define i1 @n5_wrong_pred0(i8 %x, i8 %y) {
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; CHECK-LABEL: @n5_wrong_pred0(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp uge i8 %t0, %x
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ret i1 %r
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}
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define i1 @n6_wrong_pred1(i8 %x, i8 %y) {
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; CHECK-LABEL: @n6_wrong_pred1(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp ult i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp ult i8 %t0, %x
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ret i1 %r
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}
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define i1 @n7_wrong_pred2(i8 %x, i8 %y) {
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; CHECK-LABEL: @n7_wrong_pred2(
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; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[Y:%.*]], 0
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp eq i8 %t0, %x
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ret i1 %r
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}
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define i1 @n8_wrong_pred3(i8 %x, i8 %y) {
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; CHECK-LABEL: @n8_wrong_pred3(
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; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[Y:%.*]], 0
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp ne i8 %t0, %x
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ret i1 %r
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}
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define i1 @n9_wrong_pred4(i8 %x, i8 %y) {
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; CHECK-LABEL: @n9_wrong_pred4(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp slt i8 %t0, %x
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ret i1 %r
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}
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define i1 @n10_wrong_pred5(i8 %x, i8 %y) {
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; CHECK-LABEL: @n10_wrong_pred5(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp sle i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp sle i8 %t0, %x
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ret i1 %r
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}
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define i1 @n11_wrong_pred6(i8 %x, i8 %y) {
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; CHECK-LABEL: @n11_wrong_pred6(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp sgt i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp sgt i8 %t0, %x
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ret i1 %r
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}
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define i1 @n12_wrong_pred7(i8 %x, i8 %y) {
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; CHECK-LABEL: @n12_wrong_pred7(
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; CHECK-NEXT: [[T0:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: [[R:%.*]] = icmp sge i8 [[T0]], [[X]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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%t0 = sub i8 %x, %y
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%r = icmp sge i8 %t0, %x
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ret i1 %r
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}
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