[InstSimplify] fold div/rem of zexted bool
I was looking at an unrelated fold and noticed that
we don't have this simplification (because the other
fold would break existing tests).
Name: zext udiv
%z = zext i1 %x to i32
%r = udiv i32 %y, %z
=>
%r = %y
Name: zext urem
%z = zext i1 %x to i32
%r = urem i32 %y, %z
=>
%r = 0
Name: zext sdiv
%z = zext i1 %x to i32
%r = sdiv i32 %y, %z
=>
%r = %y
Name: zext srem
%z = zext i1 %x to i32
%r = srem i32 %y, %z
=>
%r = 0
https://rise4fun.com/Alive/LZ9
llvm-svn: 335512
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index f1bfa33..4f5bed9 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -902,7 +902,10 @@
// X % 1 -> 0
// If this is a boolean op (single-bit element type), we can't have
// division-by-zero or remainder-by-zero, so assume the divisor is 1.
- if (match(Op1, m_One()) || Ty->isIntOrIntVectorTy(1))
+ // Similarly, if we're zero-extending a boolean divisor, then assume it's a 1.
+ Value *X;
+ if (match(Op1, m_One()) || Ty->isIntOrIntVectorTy(1) ||
+ (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)))
return IsDiv ? Op0 : Constant::getNullValue(Ty);
return nullptr;
diff --git a/llvm/test/Transforms/InstCombine/rem.ll b/llvm/test/Transforms/InstCombine/rem.ll
index a85b5c4..17bb9ab 100644
--- a/llvm/test/Transforms/InstCombine/rem.ll
+++ b/llvm/test/Transforms/InstCombine/rem.ll
@@ -485,11 +485,9 @@
; CHECK-NEXT: [[V:%.*]] = load volatile i32, i32* [[P:%.*]], align 4
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
-; CHECK-NEXT: [[LHS:%.*]] = phi i32 [ [[V]], [[IF_THEN]] ], [ 5, [[ENTRY:%.*]] ]
; CHECK-NEXT: br i1 icmp eq (i16* getelementptr inbounds ([5 x i16], [5 x i16]* @a, i64 0, i64 4), i16* @b), label [[REM_IS_SAFE:%.*]], label [[REM_IS_UNSAFE:%.*]]
; CHECK: rem.is.safe:
-; CHECK-NEXT: [[REM:%.*]] = srem i32 [[LHS]], zext (i1 icmp eq (i16* getelementptr inbounds ([5 x i16], [5 x i16]* @a, i64 0, i64 4), i16* @b) to i32)
-; CHECK-NEXT: ret i32 [[REM]]
+; CHECK-NEXT: ret i32 0
; CHECK: rem.is.unsafe:
; CHECK-NEXT: ret i32 0
;
@@ -555,11 +553,9 @@
; CHECK-NEXT: [[V:%.*]] = load volatile i32, i32* [[P:%.*]], align 4
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
-; CHECK-NEXT: [[LHS:%.*]] = phi i32 [ [[V]], [[IF_THEN]] ], [ 5, [[ENTRY:%.*]] ]
; CHECK-NEXT: br i1 icmp eq (i16* getelementptr inbounds ([5 x i16], [5 x i16]* @a, i64 0, i64 4), i16* @b), label [[REM_IS_SAFE:%.*]], label [[REM_IS_UNSAFE:%.*]]
; CHECK: rem.is.safe:
-; CHECK-NEXT: [[REM:%.*]] = urem i32 [[LHS]], zext (i1 icmp eq (i16* getelementptr inbounds ([5 x i16], [5 x i16]* @a, i64 0, i64 4), i16* @b) to i32)
-; CHECK-NEXT: ret i32 [[REM]]
+; CHECK-NEXT: ret i32 0
; CHECK: rem.is.unsafe:
; CHECK-NEXT: ret i32 0
;
diff --git a/llvm/test/Transforms/InstSimplify/div.ll b/llvm/test/Transforms/InstSimplify/div.ll
index 4cd2bae..a1c0556 100644
--- a/llvm/test/Transforms/InstSimplify/div.ll
+++ b/llvm/test/Transforms/InstSimplify/div.ll
@@ -97,9 +97,7 @@
define i32 @zext_bool_udiv_divisor(i1 %x, i32 %y) {
; CHECK-LABEL: @zext_bool_udiv_divisor(
-; CHECK-NEXT: [[EXT:%.*]] = zext i1 [[X:%.*]] to i32
-; CHECK-NEXT: [[R:%.*]] = udiv i32 [[Y:%.*]], [[EXT]]
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: ret i32 [[Y:%.*]]
;
%ext = zext i1 %x to i32
%r = udiv i32 %y, %ext
@@ -108,9 +106,7 @@
define <2 x i32> @zext_bool_sdiv_divisor_vec(<2 x i1> %x, <2 x i32> %y) {
; CHECK-LABEL: @zext_bool_sdiv_divisor_vec(
-; CHECK-NEXT: [[EXT:%.*]] = zext <2 x i1> [[X:%.*]] to <2 x i32>
-; CHECK-NEXT: [[R:%.*]] = sdiv <2 x i32> [[Y:%.*]], [[EXT]]
-; CHECK-NEXT: ret <2 x i32> [[R]]
+; CHECK-NEXT: ret <2 x i32> [[Y:%.*]]
;
%ext = zext <2 x i1> %x to <2 x i32>
%r = sdiv <2 x i32> %y, %ext
diff --git a/llvm/test/Transforms/InstSimplify/rem.ll b/llvm/test/Transforms/InstSimplify/rem.ll
index cf586bf..eba5b74 100644
--- a/llvm/test/Transforms/InstSimplify/rem.ll
+++ b/llvm/test/Transforms/InstSimplify/rem.ll
@@ -97,9 +97,7 @@
define <2 x i32> @zext_bool_urem_divisor_vec(<2 x i1> %x, <2 x i32> %y) {
; CHECK-LABEL: @zext_bool_urem_divisor_vec(
-; CHECK-NEXT: [[EXT:%.*]] = zext <2 x i1> [[X:%.*]] to <2 x i32>
-; CHECK-NEXT: [[R:%.*]] = urem <2 x i32> [[Y:%.*]], [[EXT]]
-; CHECK-NEXT: ret <2 x i32> [[R]]
+; CHECK-NEXT: ret <2 x i32> zeroinitializer
;
%ext = zext <2 x i1> %x to <2 x i32>
%r = urem <2 x i32> %y, %ext
@@ -108,9 +106,7 @@
define i32 @zext_bool_srem_divisor(i1 %x, i32 %y) {
; CHECK-LABEL: @zext_bool_srem_divisor(
-; CHECK-NEXT: [[EXT:%.*]] = zext i1 [[X:%.*]] to i32
-; CHECK-NEXT: [[R:%.*]] = srem i32 [[Y:%.*]], [[EXT]]
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: ret i32 0
;
%ext = zext i1 %x to i32
%r = srem i32 %y, %ext