Instcombine was illegally transforming -X/C into X/-C when either X or C

overflowed on negation. This commit checks to make sure that neithe C nor X
overflows. This requires that the RHS of X (a subtract instruction) be a
constant integer.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60275 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 32 insertions, 6 deletions

diff --git a/test/Transforms/InstCombine/apint-sub.ll b/test/Transforms/InstCombine/apint-sub.ll
index 12f366de7f..2ff763c9f5 100644
--- a/test/Transforms/InstCombine/apint-sub.ll
+++ b/test/Transforms/InstCombine/apint-sub.ll
@@ -3,7 +3,7 @@
 ;
 
 ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | \
-; RUN:   grep -v {sub i19 %Cok, %Bok} | not grep sub
+; RUN:   grep -v {sub i19 %Cok, %Bok} | grep -v {sub i25 0, %Aok} | not grep sub
 ; END.
 
 define i23 @test1(i23 %A) {
@@ -107,8 +107,10 @@ define i51 @test16(i51 %A) {
 	ret i51 %Y
 }
 
-define i25 @test17(i25 %A) {
-	%B = sub i25 0, %A		; <i25> [#uses=1]
+; Can't fold subtract here because negation it might oveflow.
+; PR3142
+define i25 @test17(i25 %Aok) {
+	%B = sub i25 0, %Aok		; <i25> [#uses=1]
 	%C = sdiv i25 %B, 1234		; <i25> [#uses=1]
 	ret i25 %C
 }
diff --git a/test/Transforms/InstCombine/sdiv-1.ll b/test/Transforms/InstCombine/sdiv-1.ll
new file mode 100644
index 0000000000..c10bd77515
--- /dev/null
+++ b/test/Transforms/InstCombine/sdiv-1.ll
@@ -0,0 +1,22 @@
+; RUN: llvm-as < %s | opt -instcombine -inline | llvm-dis | grep {715827882} | count 2
+; PR3142
+
+define i32 @a(i32 %X) nounwind readnone {
+entry:
+       %0 = sub i32 0, %X
+       %1 = sdiv i32 %0, -3
+       ret i32 %1
+}
+
+define i32 @b(i32 %X) nounwind readnone {
+entry:
+       %0 = call i32 @a(i32 -2147483648)
+       ret i32 %0
+}
+
+define i32 @c(i32 %X) nounwind readnone {
+entry:
+       %0 = sub i32 0, -2147483648
+       %1 = sdiv i32 %0, -3
+       ret i32 %1
+}
diff --git a/test/Transforms/InstCombine/sub.ll b/test/Transforms/InstCombine/sub.ll
index da6d710f6b..1ab4eaf1b4 100644
--- a/test/Transforms/InstCombine/sub.ll
+++ b/test/Transforms/InstCombine/sub.ll
@@ -1,7 +1,7 @@
 ; This test makes sure that these instructions are properly eliminated.
 ;
 ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | \
-; RUN:   grep -v {sub i32 %Cok, %Bok} | not grep sub
+; RUN:   grep -v {sub i32 %Cok, %Bok} | grep -v {sub i32 0, %Aok} | not grep sub
 
 define i32 @test1(i32 %A) {
 	%B = sub i32 %A, %A		; <i32> [#uses=1]
@@ -104,8 +104,10 @@ define i32 @test16(i32 %A) {
 	ret i32 %Y
 }
 
-define i32 @test17(i32 %A) {
-	%B = sub i32 0, %A		; <i32> [#uses=1]
+; Can't fold subtract here because negation it might oveflow.
+; PR3142
+define i32 @test17(i32 %Aok) {
+	%B = sub i32 0, %Aok		; <i32> [#uses=1]
 	%C = sdiv i32 %B, 1234		; <i32> [#uses=1]
 	ret i32 %C
 }