[InstCombine] use commutative matchers for patterns with commutative operators

Background/motivation - I was circling back around to:
https://llvm.org/bugs/show_bug.cgi?id=28296

I made a simple patch for that and noticed some regressions, so added test cases for
those with rL281055, and this is hopefully the minimal fix for just those cases.

But as you can see from the surrounding untouched folds, we are missing commuted patterns
all over the place, and of course there are no regression tests to cover any of those cases.

We could sprinkle "m_c_" dust all over this file and catch most of the missing folds, but 
then we still wouldn't have test coverage, and we'd still miss some fraction of commuted 
patterns because they require adjustments to the match order.

I'm aware of the concern about the potential compile-time performance impact of adding 
matches like this (currently being discussed on llvm-dev), but I don't think there's any
evidence yet to suggest that handling commutative pattern matching more thoroughly is not
a worthwhile goal of InstCombine.

Differential Revision: https://reviews.llvm.org/D24419

llvm-svn: 290067

3 files changed, 13 insertions, 51 deletions

diff --git a/llvm/test/Transforms/InstCombine/or-xor.ll b/llvm/test/Transforms/InstCombine/or-xor.ll
index 3ba51de7108..ec5b71656a4 100644
--- a/llvm/test/Transforms/InstCombine/or-xor.ll
+++ b/llvm/test/Transforms/InstCombine/or-xor.ll
@@ -140,14 +140,9 @@ define i32 @test12(i32 %x, i32 %y) {
   ret i32 %and
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test12_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test12_commuted(
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 %x, -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[NEG]], %y
-; CHECK-NEXT:    [[OR:%.*]] = or i32 %y, %x
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[XOR]], [[OR]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 %x, %y
 ; CHECK-NEXT:    ret i32 [[AND]]
 ;
   %neg = xor i32 %x, -1
@@ -183,15 +178,9 @@ define i32 @test14(i32 %x, i32 %y) {
   ret i32 %xor
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test14_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test14_commuted(
-; CHECK-NEXT:    [[NOTY:%.*]] = xor i32 %y, -1
-; CHECK-NEXT:    [[NOTX:%.*]] = xor i32 %x, -1
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[NOTY]], %x
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[NOTX]], %y
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 %x, %y
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -216,15 +205,9 @@ define i32 @test15(i32 %x, i32 %y) {
   ret i32 %xor
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test15_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test15_commuted(
-; CHECK-NEXT:    [[NOTY:%.*]] = xor i32 %y, -1
-; CHECK-NEXT:    [[NOTX:%.*]] = xor i32 %x, -1
-; CHECK-NEXT:    [[AND1:%.*]] = and i32 [[NOTY]], %x
-; CHECK-NEXT:    [[AND2:%.*]] = and i32 [[NOTX]], %y
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 %x, %y
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
diff --git a/llvm/test/Transforms/InstCombine/or.ll b/llvm/test/Transforms/InstCombine/or.ll
index 38b8ebc5adf..facd63019fe 100644
--- a/llvm/test/Transforms/InstCombine/or.ll
+++ b/llvm/test/Transforms/InstCombine/or.ll
@@ -570,14 +570,10 @@ define i32 @test42(i32 %a, i32 %b) {
   ret i32 %or
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test42_commuted_and(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test42_commuted_and(
-; CHECK-NEXT:    [[NEGA:%.*]] = xor i32 %a, -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[NEGA]], %b
-; CHECK-NEXT:    [[AND:%.*]] = and i32 %b, %a
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[XOR]], [[AND]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 %a, -1
+; CHECK-NEXT:    [[OR:%.*]] = xor i32 [[TMP1]], %b
 ; CHECK-NEXT:    ret i32 [[OR]]
 ;
   %nega = xor i32 %a, -1
@@ -587,14 +583,10 @@ define i32 @test42_commuted_and(i32 %a, i32 %b) {
   ret i32 %or
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test42_commuted_xor(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test42_commuted_xor(
-; CHECK-NEXT:    [[NEGA:%.*]] = xor i32 %a, -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 %b, [[NEGA]]
-; CHECK-NEXT:    [[AND:%.*]] = and i32 %a, %b
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[XOR]], [[AND]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 %a, -1
+; CHECK-NEXT:    [[OR:%.*]] = xor i32 [[TMP1]], %b
 ; CHECK-NEXT:    ret i32 [[OR]]
 ;
   %nega = xor i32 %a, -1
@@ -618,14 +610,9 @@ define i32 @test43(i32 %a, i32 %b) {
   ret i32 %or
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test43_commuted_and(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test43_commuted_and(
-; CHECK-NEXT:    [[NEG:%.*]] = xor i32 %b, -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NEG]], %a
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 %a, %b
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[AND]], [[XOR]]
+; CHECK-NEXT:    [[OR:%.*]] = xor i32 %a, %b
 ; CHECK-NEXT:    ret i32 [[OR]]
 ;
   %neg = xor i32 %b, -1
diff --git a/llvm/test/Transforms/InstCombine/xor2.ll b/llvm/test/Transforms/InstCombine/xor2.ll
index 7ec84d8caf9..f3591ed9c8a 100644
--- a/llvm/test/Transforms/InstCombine/xor2.ll
+++ b/llvm/test/Transforms/InstCombine/xor2.ll
@@ -180,14 +180,10 @@ define i32 @test12(i32 %a, i32 %b) {
   ret i32 %xor
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test12commuted(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test12commuted(
-; CHECK-NEXT:    [[NEGB:%.*]] = xor i32 %b, -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NEGB]], %a
-; CHECK-NEXT:    [[NEGA:%.*]] = xor i32 %a, -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[AND]], [[NEGA]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 %a, %b
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %negb = xor i32 %b, -1
@@ -198,7 +194,7 @@ define i32 @test12commuted(i32 %a, i32 %b) {
 }
 
 ; This is a test of canonicalization via operand complexity.
-; The final xor has a binary operator and a (fake) unary operator, 
+; The final xor has a binary operator and a (fake) unary operator,
 ; so binary (more complex) should come first.
 
 define i32 @test13(i32 %a, i32 %b) {
@@ -214,14 +210,10 @@ define i32 @test13(i32 %a, i32 %b) {
   ret i32 %xor
 }
 
-; FIXME: We miss the fold because the pattern matching is inadequate.
-
 define i32 @test13commuted(i32 %a, i32 %b) {
 ; CHECK-LABEL: @test13commuted(
-; CHECK-NEXT:    [[NEGA:%.*]] = xor i32 %a, -1
-; CHECK-NEXT:    [[NEGB:%.*]] = xor i32 %b, -1
-; CHECK-NEXT:    [[AND:%.*]] = and i32 [[NEGB]], %a
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[AND]], [[NEGA]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 %a, %b
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %nega = xor i32 %a, -1