[llvm] r285075 - [InstCombine] add test and code comment to show potentially misguided icmp trunc transform
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 25 08:16:39 PDT 2016
Author: spatel
Date: Tue Oct 25 10:16:39 2016
New Revision: 285075
URL: http://llvm.org/viewvc/llvm-project?rev=285075&view=rev
Log:
[InstCombine] add test and code comment to show potentially misguided icmp trunc transform
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/icmp.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=285075&r1=285074&r2=285075&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Tue Oct 25 10:16:39 2016
@@ -1950,6 +1950,9 @@ Instruction *InstCombiner::foldICmpShlCo
And, Constant::getNullValue(And->getType()));
}
+ // FIXME: This transform can create illegal types. Use the DataLayout to
+ // decide when to try this?
+
// Transform (icmp pred iM (shl iM %v, N), C)
// -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
// Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=285075&r1=285074&r2=285075&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Tue Oct 25 10:16:39 2016
@@ -1208,6 +1208,19 @@ define i1 @icmp_shl16(i32 %x) {
ret i1 %cmp
}
+; FIXME: We shouldn't be creating illegal types like i15 in InstCombine.
+
+define i1 @icmp_shl17(i32 %x) {
+; CHECK-LABEL: @icmp_shl17(
+; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 %x to i15
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i15 [[TMP1]], 18
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %shl = shl i32 %x, 17
+ %cmp = icmp slt i32 %shl, 2359296
+ ret i1 %cmp
+}
+
define <2 x i1> @icmp_shl16_vec(<2 x i32> %x) {
; CHECK-LABEL: @icmp_shl16_vec(
; CHECK-NEXT: [[TMP1:%.*]] = trunc <2 x i32> %x to <2 x i16>
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