[llvm] r371100 - [InstCombine] foldICmpBinOp(): consider inverted check in 'unsigned add overflow' check
Roman Lebedev via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 5 10:40:49 PDT 2019
Author: lebedevri
Date: Thu Sep 5 10:40:49 2019
New Revision: 371100
URL: http://llvm.org/viewvc/llvm-project?rev=371100&view=rev
Log:
[InstCombine] foldICmpBinOp(): consider inverted check in 'unsigned add overflow' check
A follow-up for r342004.
This will be changed to produce @llvm.add.with.overflow in a later patch,
but for now just make things more consistent overall.
https://rise4fun.com/Alive/qxE
Name: (Op1 + X) u< Op1 --> ~Op1 u< X
%t0 = add i8 %Op1, %X
%r = icmp ult i8 %t0, %Op1
=>
%n = xor i8 %Op1, -1
%r = icmp ult i8 %n, %X
Name: (Op1 + X) u>= Op1 --> ~Op1 u>= X
%t0 = add i8 %Op1, %X
%r = icmp uge i8 %t0, %Op1
=>
%n = xor i8 %Op1, -1
%r = icmp uge i8 %n, %X
;-------------------------------------------------------------------------------
Name: Op0 u> (Op0 + X) --> X u> ~Op0
%t0 = add i8 %Op0, %X
%r = icmp ugt i8 %Op0, %t0
=>
%n = xor i8 %Op0, -1
%r = icmp ugt i8 %X, %n
Name: Op0 u<= (Op0 + X) --> X u<= ~Op0
%t0 = add i8 %Op0, %X
%r = icmp ule i8 %Op0, %t0
=>
%n = xor i8 %Op0, -1
%r = icmp ule i8 %X, %n
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/unsigned-add-lack-of-overflow-check.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=371100&r1=371099&r2=371100&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Thu Sep 5 10:40:49 2019
@@ -3609,13 +3609,13 @@ Instruction *InstCombiner::foldICmpBinOp
Value *X;
// Convert add-with-unsigned-overflow comparisons into a 'not' with compare.
- // (Op1 + X) <u Op1 --> ~Op1 <u X
- // Op0 >u (Op0 + X) --> X >u ~Op0
+ // (Op1 + X) u</u>= Op1 --> ~Op1 u</u>= X
if (match(Op0, m_OneUse(m_c_Add(m_Specific(Op1), m_Value(X)))) &&
- Pred == ICmpInst::ICMP_ULT)
+ (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE))
return new ICmpInst(Pred, Builder.CreateNot(Op1), X);
+ // Op0 u>/u<= (Op0 + X) --> X u>/u<= ~Op0
if (match(Op1, m_OneUse(m_c_Add(m_Specific(Op0), m_Value(X)))) &&
- Pred == ICmpInst::ICMP_UGT)
+ (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULE))
return new ICmpInst(Pred, X, Builder.CreateNot(Op0));
bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
Modified: llvm/trunk/test/Transforms/InstCombine/unsigned-add-lack-of-overflow-check.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/unsigned-add-lack-of-overflow-check.ll?rev=371100&r1=371099&r2=371100&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/unsigned-add-lack-of-overflow-check.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/unsigned-add-lack-of-overflow-check.ll Thu Sep 5 10:40:49 2019
@@ -10,8 +10,8 @@
define i1 @t0_basic(i8 %x, i8 %y) {
; CHECK-LABEL: @t0_basic(
-; CHECK-NEXT: [[T0:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[T0]], [[Y]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%t0 = add i8 %x, %y
@@ -21,8 +21,8 @@ define i1 @t0_basic(i8 %x, i8 %y) {
define <2 x i1> @t1_vec(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @t1_vec(
-; CHECK-NEXT: [[T0:%.*]] = add <2 x i8> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge <2 x i8> [[T0]], [[Y]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i8> [[Y:%.*]], <i8 -1, i8 -1>
+; CHECK-NEXT: [[R:%.*]] = icmp uge <2 x i8> [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret <2 x i1> [[R]]
;
%t0 = add <2 x i8> %x, %y
@@ -34,8 +34,8 @@ define <2 x i1> @t1_vec(<2 x i8> %x, <2
define i1 @t2_symmetry(i8 %x, i8 %y) {
; CHECK-LABEL: @t2_symmetry(
-; CHECK-NEXT: [[T0:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[T0]], [[X]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[X:%.*]], -1
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP1]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%t0 = add i8 %x, %y
@@ -48,8 +48,8 @@ declare i8 @gen8()
define i1 @t3_commutative(i8 %x) {
; CHECK-LABEL: @t3_commutative(
; CHECK-NEXT: [[Y:%.*]] = call i8 @gen8()
-; CHECK-NEXT: [[T0:%.*]] = add i8 [[Y]], [[X:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[T0]], [[Y]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y]], -1
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = call i8 @gen8()
@@ -60,8 +60,8 @@ define i1 @t3_commutative(i8 %x) {
define i1 @t4_commutative(i8 %x, i8 %y) {
; CHECK-LABEL: @t4_commutative(
-; CHECK-NEXT: [[T0:%.*]] = add i8 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[T0]], [[Y]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y:%.*]], -1
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%t0 = add i8 %x, %y
@@ -72,8 +72,8 @@ define i1 @t4_commutative(i8 %x, i8 %y)
define i1 @t5_commutative(i8 %x) {
; CHECK-LABEL: @t5_commutative(
; CHECK-NEXT: [[Y:%.*]] = call i8 @gen8()
-; CHECK-NEXT: [[T0:%.*]] = add i8 [[Y]], [[X:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp ule i8 [[Y]], [[T0]]
+; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[Y]], -1
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = call i8 @gen8()
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