[PatternMatch] add special-case uaddo matching for increment-by-one

This is the most important uaddo problem mentioned in PR31754:
https://bugs.llvm.org/show_bug.cgi?id=31754

We were failing to match the canonicalized pattern when it's an 'add 1' operation.
Pattern matching, however, shouldn't assume that we have canonicalized IR, so we 
match 4 commuted variants of uaddo.

There's also a test with a crazy type to show that the existing CGP transform 
based on this matcher is not limited by target legality checks, but that's a
different problem.

Differential Revision: https://reviews.llvm.org/D57516

llvm-svn: 352766

3 files changed, 40 insertions, 23 deletions

diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index 1f1a37d4304..6c51d487737 100644
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -1463,6 +1463,20 @@ struct UAddWithOverflow_match {
       if (AddExpr.match(ICmpRHS) && (ICmpLHS == AddLHS || ICmpLHS == AddRHS))
         return L.match(AddLHS) && R.match(AddRHS) && S.match(ICmpRHS);
 
+    // Match special-case for increment-by-1.
+    if (Pred == ICmpInst::ICMP_EQ) {
+      // (a + 1) == 0
+      // (1 + a) == 0
+      if (AddExpr.match(ICmpLHS) && m_ZeroInt().match(ICmpRHS) &&
+          (m_One().match(AddLHS) || m_One().match(AddRHS)))
+        return L.match(AddLHS) && R.match(AddRHS) && S.match(ICmpLHS);
+      // 0 == (a + 1)
+      // 0 == (1 + a)
+      if (m_ZeroInt().match(ICmpLHS) && AddExpr.match(ICmpRHS) &&
+          (m_One().match(AddLHS) || m_One().match(AddRHS)))
+        return L.match(AddLHS) && R.match(AddRHS) && S.match(ICmpRHS);
+    }
+
     return false;
   }
 };
diff --git a/llvm/test/CodeGen/X86/codegen-prepare-uaddo.ll b/llvm/test/CodeGen/X86/codegen-prepare-uaddo.ll
index 52dfe1c8792..1ac9eb24440 100644
--- a/llvm/test/CodeGen/X86/codegen-prepare-uaddo.ll
+++ b/llvm/test/CodeGen/X86/codegen-prepare-uaddo.ll
@@ -42,9 +42,7 @@ define void @test_0(i64*, i64*) {
 define void @test_1(i64*, i64*) {
 ; CHECK-LABEL: test_1:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    incq (%rdi)
-; CHECK-NEXT:    sete %al
-; CHECK-NEXT:    addb $-1, %al
+; CHECK-NEXT:    addq $1, (%rdi)
 ; CHECK-NEXT:    adcq $0, (%rsi)
 ; CHECK-NEXT:    retq
   %3 = load i64, i64* %0, align 8
diff --git a/llvm/test/Transforms/CodeGenPrepare/overflow-intrinsics.ll b/llvm/test/Transforms/CodeGenPrepare/overflow-intrinsics.ll
index d3d23768980..6b91a3b3c18 100644
--- a/llvm/test/Transforms/CodeGenPrepare/overflow-intrinsics.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/overflow-intrinsics.ll
@@ -105,10 +105,11 @@ exit:
 
 define i1 @uaddo_i64_increment(i64 %x, i64* %p) {
 ; CHECK-LABEL: @uaddo_i64_increment(
-; CHECK-NEXT:    [[A:%.*]] = add i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[OV:%.*]] = icmp eq i64 [[A]], 0
-; CHECK-NEXT:    store i64 [[A]], i64* [[P:%.*]]
-; CHECK-NEXT:    ret i1 [[OV]]
+; CHECK-NEXT:    [[UADD_OVERFLOW:%.*]] = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 [[X:%.*]], i64 1)
+; CHECK-NEXT:    [[UADD:%.*]] = extractvalue { i64, i1 } [[UADD_OVERFLOW]], 0
+; CHECK-NEXT:    [[OVERFLOW:%.*]] = extractvalue { i64, i1 } [[UADD_OVERFLOW]], 1
+; CHECK-NEXT:    store i64 [[UADD]], i64* [[P:%.*]]
+; CHECK-NEXT:    ret i1 [[OVERFLOW]]
 ;
   %a = add i64 %x, 1
   %ov = icmp eq i64 %a, 0
@@ -118,10 +119,11 @@ define i1 @uaddo_i64_increment(i64 %x, i64* %p) {
 
 define i1 @uaddo_i8_increment_noncanonical_1(i8 %x, i8* %p) {
 ; CHECK-LABEL: @uaddo_i8_increment_noncanonical_1(
-; CHECK-NEXT:    [[A:%.*]] = add i8 1, [[X:%.*]]
-; CHECK-NEXT:    [[OV:%.*]] = icmp eq i8 [[A]], 0
-; CHECK-NEXT:    store i8 [[A]], i8* [[P:%.*]]
-; CHECK-NEXT:    ret i1 [[OV]]
+; CHECK-NEXT:    [[UADD_OVERFLOW:%.*]] = call { i8, i1 } @llvm.uadd.with.overflow.i8(i8 1, i8 [[X:%.*]])
+; CHECK-NEXT:    [[UADD:%.*]] = extractvalue { i8, i1 } [[UADD_OVERFLOW]], 0
+; CHECK-NEXT:    [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[UADD_OVERFLOW]], 1
+; CHECK-NEXT:    store i8 [[UADD]], i8* [[P:%.*]]
+; CHECK-NEXT:    ret i1 [[OVERFLOW]]
 ;
   %a = add i8 1, %x        ; commute
   %ov = icmp eq i8 %a, 0
@@ -131,10 +133,11 @@ define i1 @uaddo_i8_increment_noncanonical_1(i8 %x, i8* %p) {
 
 define i1 @uaddo_i32_increment_noncanonical_2(i32 %x, i32* %p) {
 ; CHECK-LABEL: @uaddo_i32_increment_noncanonical_2(
-; CHECK-NEXT:    [[A:%.*]] = add i32 [[X:%.*]], 1
-; CHECK-NEXT:    [[OV:%.*]] = icmp eq i32 0, [[A]]
-; CHECK-NEXT:    store i32 [[A]], i32* [[P:%.*]]
-; CHECK-NEXT:    ret i1 [[OV]]
+; CHECK-NEXT:    [[UADD_OVERFLOW:%.*]] = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 [[X:%.*]], i32 1)
+; CHECK-NEXT:    [[UADD:%.*]] = extractvalue { i32, i1 } [[UADD_OVERFLOW]], 0
+; CHECK-NEXT:    [[OVERFLOW:%.*]] = extractvalue { i32, i1 } [[UADD_OVERFLOW]], 1
+; CHECK-NEXT:    store i32 [[UADD]], i32* [[P:%.*]]
+; CHECK-NEXT:    ret i1 [[OVERFLOW]]
 ;
   %a = add i32 %x, 1
   %ov = icmp eq i32 0, %a   ; commute
@@ -144,10 +147,11 @@ define i1 @uaddo_i32_increment_noncanonical_2(i32 %x, i32* %p) {
 
 define i1 @uaddo_i16_increment_noncanonical_3(i16 %x, i16* %p) {
 ; CHECK-LABEL: @uaddo_i16_increment_noncanonical_3(
-; CHECK-NEXT:    [[A:%.*]] = add i16 1, [[X:%.*]]
-; CHECK-NEXT:    [[OV:%.*]] = icmp eq i16 0, [[A]]
-; CHECK-NEXT:    store i16 [[A]], i16* [[P:%.*]]
-; CHECK-NEXT:    ret i1 [[OV]]
+; CHECK-NEXT:    [[UADD_OVERFLOW:%.*]] = call { i16, i1 } @llvm.uadd.with.overflow.i16(i16 1, i16 [[X:%.*]])
+; CHECK-NEXT:    [[UADD:%.*]] = extractvalue { i16, i1 } [[UADD_OVERFLOW]], 0
+; CHECK-NEXT:    [[OVERFLOW:%.*]] = extractvalue { i16, i1 } [[UADD_OVERFLOW]], 1
+; CHECK-NEXT:    store i16 [[UADD]], i16* [[P:%.*]]
+; CHECK-NEXT:    ret i1 [[OVERFLOW]]
 ;
   %a = add i16 1, %x        ; commute
   %ov = icmp eq i16 0, %a   ; commute
@@ -159,10 +163,11 @@ define i1 @uaddo_i16_increment_noncanonical_3(i16 %x, i16* %p) {
 
 define i1 @uaddo_i42_increment_illegal_type(i42 %x, i42* %p) {
 ; CHECK-LABEL: @uaddo_i42_increment_illegal_type(
-; CHECK-NEXT:    [[A:%.*]] = add i42 [[X:%.*]], 1
-; CHECK-NEXT:    [[OV:%.*]] = icmp eq i42 [[A]], 0
-; CHECK-NEXT:    store i42 [[A]], i42* [[P:%.*]]
-; CHECK-NEXT:    ret i1 [[OV]]
+; CHECK-NEXT:    [[UADD_OVERFLOW:%.*]] = call { i42, i1 } @llvm.uadd.with.overflow.i42(i42 [[X:%.*]], i42 1)
+; CHECK-NEXT:    [[UADD:%.*]] = extractvalue { i42, i1 } [[UADD_OVERFLOW]], 0
+; CHECK-NEXT:    [[OVERFLOW:%.*]] = extractvalue { i42, i1 } [[UADD_OVERFLOW]], 1
+; CHECK-NEXT:    store i42 [[UADD]], i42* [[P:%.*]]
+; CHECK-NEXT:    ret i1 [[OVERFLOW]]
 ;
   %a = add i42 %x, 1
   %ov = icmp eq i42 %a, 0