[InstCombine] fold add(zext(xor X, C), C) --> sext X when C is INT_MIN in the source type
The pattern may look more obviously like a sext if written as:
define i32 @g(i16 %x) {
%zext = zext i16 %x to i32
%xor = xor i32 %zext, 32768
%add = add i32 %xor, -32768
ret i32 %add
}
We already have that fold in visitAdd().
Differential Revision: https://reviews.llvm.org/D22477
llvm-svn: 276035
diff --git a/llvm/test/Transforms/InstCombine/apint-add.ll b/llvm/test/Transforms/InstCombine/apint-add.ll
index f5b5bcb..c55fd04 100644
--- a/llvm/test/Transforms/InstCombine/apint-add.ll
+++ b/llvm/test/Transforms/InstCombine/apint-add.ll
@@ -56,9 +56,7 @@
define i7 @sext(i4 %x) {
; CHECK-LABEL: @sext(
-; CHECK-NEXT: [[XOR:%.*]] = xor i4 %x, -8
-; CHECK-NEXT: [[ZEXT:%.*]] = zext i4 [[XOR]] to i7
-; CHECK-NEXT: [[ADD:%.*]] = add nsw i7 [[ZEXT]], -8
+; CHECK-NEXT: [[ADD:%.*]] = sext i4 %x to i7
; CHECK-NEXT: ret i7 [[ADD]]
;
%xor = xor i4 %x, -8
@@ -69,9 +67,7 @@
define <2 x i10> @sext_vec(<2 x i3> %x) {
; CHECK-LABEL: @sext_vec(
-; CHECK-NEXT: [[XOR:%.*]] = xor <2 x i3> %x, <i3 -4, i3 -4>
-; CHECK-NEXT: [[ZEXT:%.*]] = zext <2 x i3> [[XOR]] to <2 x i10>
-; CHECK-NEXT: [[ADD:%.*]] = add nsw <2 x i10> [[ZEXT]], <i10 -4, i10 -4>
+; CHECK-NEXT: [[ADD:%.*]] = sext <2 x i3> %x to <2 x i10>
; CHECK-NEXT: ret <2 x i10> [[ADD]]
;
%xor = xor <2 x i3> %x, <i3 -4, i3 -4>
@@ -80,6 +76,27 @@
ret <2 x i10> %add
}
+; Multiple uses of the operands don't prevent the fold.
+
+define i4 @sext_multiuse(i4 %x) {
+; CHECK-LABEL: @sext_multiuse(
+; CHECK-NEXT: [[XOR:%.*]] = xor i4 %x, -8
+; CHECK-NEXT: [[ZEXT:%.*]] = zext i4 [[XOR]] to i7
+; CHECK-NEXT: [[ADD:%.*]] = sext i4 %x to i7
+; CHECK-NEXT: [[MUL:%.*]] = sdiv i7 [[ZEXT]], [[ADD]]
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i7 [[MUL]] to i4
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i4 [[TRUNC]], [[XOR]]
+; CHECK-NEXT: ret i4 [[DIV]]
+;
+ %xor = xor i4 %x, -8
+ %zext = zext i4 %xor to i7
+ %add = add nsw i7 %zext, -8
+ %mul = sdiv i7 %zext, %add
+ %trunc = trunc i7 %mul to i4
+ %div = sdiv i4 %trunc, %xor
+ ret i4 %div
+}
+
; Tests for Integer BitWidth > 64 && BitWidth <= 1024.
;; Flip sign bit then add INT_MIN -> nop.