[ValueTracking] Look through casts when both operands are casts.
We only looked through casts when one operand was a constant. We can also look through casts when both operands are non-constant, but both are in fact the same cast type. For example:
%1 = icmp ult i8 %a, %b
%2 = zext i8 %a to i32
%3 = zext i8 %b to i32
%4 = select i1 %1, i32 %2, i32 %3
llvm-svn: 246678
diff --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index b5ad019..1512ad0 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -146,3 +146,45 @@
// But this should be, because we've ignored signed zeroes.
expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, true});
}
+
+TEST_F(MatchSelectPatternTest, DoubleCastU) {
+ parseAssembly(
+ "define i32 @test(i8 %a, i8 %b) {\n"
+ " %1 = icmp ult i8 %a, %b\n"
+ " %2 = zext i8 %a to i32\n"
+ " %3 = zext i8 %b to i32\n"
+ " %A = select i1 %1, i32 %2, i32 %3\n"
+ " ret i32 %A\n"
+ "}\n");
+ // We should be able to look through the situation where we cast both operands
+ // to the select.
+ expectPattern({SPF_UMIN, SPNB_NA, false});
+}
+
+TEST_F(MatchSelectPatternTest, DoubleCastS) {
+ parseAssembly(
+ "define i32 @test(i8 %a, i8 %b) {\n"
+ " %1 = icmp slt i8 %a, %b\n"
+ " %2 = sext i8 %a to i32\n"
+ " %3 = sext i8 %b to i32\n"
+ " %A = select i1 %1, i32 %2, i32 %3\n"
+ " ret i32 %A\n"
+ "}\n");
+ // We should be able to look through the situation where we cast both operands
+ // to the select.
+ expectPattern({SPF_SMIN, SPNB_NA, false});
+}
+
+TEST_F(MatchSelectPatternTest, DoubleCastBad) {
+ parseAssembly(
+ "define i32 @test(i8 %a, i8 %b) {\n"
+ " %1 = icmp ult i8 %a, %b\n"
+ " %2 = zext i8 %a to i32\n"
+ " %3 = sext i8 %b to i32\n"
+ " %A = select i1 %1, i32 %2, i32 %3\n"
+ " ret i32 %A\n"
+ "}\n");
+ // We should be able to look through the situation where we cast both operands
+ // to the select.
+ expectPattern({SPF_UNKNOWN, SPNB_NA, false});
+}