[PATCH] D49365: [InstrSimplify] add testcases for fold sdiv if two operands are negatived and non-overflow
ChenZheng via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 16 02:05:25 PDT 2018
shchenz created this revision.
shchenz added reviewers: spatel, nemanjai.
shchenz edited the summary of this revision.
We add folding support for add instruction in https://reviews.llvm.org/D49216.
we should also fold for sdiv instruction if sdiv's two operands are negatived leverage new added interface isKnownNegation() in https://reviews.llvm.org/D49216. for example:
define i32 @negated_operand(i32 %x) {
%negx = sub nsw i32 0, %x
%div = sdiv i32 %negx, %x
ret i32 %div
}
can be folded to
define i32 @negated_operand(i32 %x) {
ret i32 -1
}
Note: we must ensure sdiv two operands are non-overflow. Otherwise, the optimization is not right.
Result from Alive:
testing transform:
%sub = sub i8 0, %x
%div = sdiv i8 %x, %sub
=>
%div = i8 -1
testing result:
ERROR: Mismatch in values of i8 %div
Example:
%x i8 = 0x80 (128, -128)
%sub i8 = 0x80 (128, -128)
Source value: 0x01 (1)
Target value: 0xFF (255, -1)
https://reviews.llvm.org/D49365
Files:
llvm/test/Transforms/InstCombine/sdiv.ll
Index: llvm/test/Transforms/InstCombine/sdiv.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/sdiv.ll
@@ -0,0 +1,49 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define i32 @negated_operand(i32 %x) {
+; CHECK-LABEL: @negated_operand(
+; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X:%.*]]
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[NEGX]], [[X]]
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %negx = sub nsw i32 0, %x
+ %div = sdiv i32 %negx, %x
+ ret i32 %div
+}
+
+define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
+; CHECK-LABEL: @negated_operand_commute_vec(
+; CHECK-NEXT: [[NEGX:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT: [[DIV:%.*]] = sdiv <2 x i32> [[NEGX]], [[X]]
+; CHECK-NEXT: ret <2 x i32> [[DIV]]
+;
+ %negx = sub nsw <2 x i32> zeroinitializer, %x
+ %div = sdiv <2 x i32> %negx, %x
+ ret <2 x i32> %div
+}
+
+define i32 @knownnegation(i32 %x, i32 %y) {
+; CHECK-LABEL: @knownnegation(
+; CHECK-NEXT: [[XY:%.*]] = sub nsw i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[YX:%.*]] = sub nsw i32 [[Y]], [[X]]
+; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[XY]], [[YX]]
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %xy = sub nsw i32 %x, %y
+ %yx = sub nsw i32 %y, %x
+ %div = sdiv i32 %xy, %yx
+ ret i32 %div
+}
+
+define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec(
+; CHECK-NEXT: [[XY:%.*]] = sub nsw <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: [[YX:%.*]] = sub nsw <2 x i32> [[Y]], [[X]]
+; CHECK-NEXT: [[DIV:%.*]] = sdiv <2 x i32> [[XY]], [[YX]]
+; CHECK-NEXT: ret <2 x i32> [[DIV]]
+;
+ %xy = sub nsw <2 x i32> %x, %y
+ %yx = sub nsw <2 x i32> %y, %x
+ %div = sdiv <2 x i32> %xy, %yx
+ ret <2 x i32> %div
+}
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