InstCombine: fold more cases of (fp_to_u/sint (u/sint_to_fp val))

Fixes radar 15486701.

From: Fiona Glaser <fglaser@apple.com>
llvm-svn: 229437

1 files changed, 110 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/sitofp.ll b/llvm/test/Transforms/InstCombine/sitofp.ll
index 48c0d71e783..82097783883 100644
--- a/llvm/test/Transforms/InstCombine/sitofp.ll
+++ b/llvm/test/Transforms/InstCombine/sitofp.ll
@@ -72,3 +72,113 @@ define i32 @test8(i32 %A) nounwind {
   ret i32 %C
 }
 
+; CHECK-LABEL: test9
+; CHECK: zext i8
+; CHECK-NEXT: ret i32
+define i32 @test9(i8 %A) nounwind {
+  %B = sitofp i8 %A to float
+  %C = fptoui float %B to i32
+  ret i32 %C
+}
+
+; CHECK-LABEL: test10
+; CHECK: sext i8
+; CHECK-NEXT: ret i32
+define i32 @test10(i8 %A) nounwind {
+  %B = sitofp i8 %A to float
+  %C = fptosi float %B to i32
+  ret i32 %C
+}
+
+; If the input value is outside of the range of the output cast, it's
+; undefined behavior, so we can assume it fits.
+; CHECK-LABEL: test11
+; CHECK: trunc
+; CHECK-NEXT: ret i8
+define i8 @test11(i32 %A) nounwind {
+  %B = sitofp i32 %A to float
+  %C = fptosi float %B to i8
+  ret i8 %C
+}
+
+; If the input value is negative, it'll be outside the range of the
+; output cast, and thus undefined behavior.
+; CHECK-LABEL: test12
+; CHECK: zext i8
+; CHECK-NEXT: ret i32
+define i32 @test12(i8 %A) nounwind {
+  %B = sitofp i8 %A to float
+  %C = fptoui float %B to i32
+  ret i32 %C
+}
+
+; This can't fold because the 25-bit input doesn't fit in the mantissa.
+; CHECK-LABEL: test13
+; CHECK: uitofp
+; CHECK-NEXT: fptoui
+define i32 @test13(i25 %A) nounwind {
+  %B = uitofp i25 %A to float
+  %C = fptoui float %B to i32
+  ret i32 %C
+}
+
+; But this one can.
+; CHECK-LABEL: test14
+; CHECK: zext i24
+; CHECK-NEXT: ret i32
+define i32 @test14(i24 %A) nounwind {
+  %B = uitofp i24 %A to float
+  %C = fptoui float %B to i32
+  ret i32 %C
+}
+
+; And this one can too.
+; CHECK-LABEL: test15
+; CHECK: trunc i32
+; CHECK-NEXT: ret i24
+define i24 @test15(i32 %A) nounwind {
+  %B = uitofp i32 %A to float
+  %C = fptoui float %B to i24
+  ret i24 %C
+}
+
+; This can fold because the 25-bit input is signed and we disard the sign bit.
+; CHECK-LABEL: test16
+; CHECK: zext
+define i32 @test16(i25 %A) nounwind {
+ %B = sitofp i25 %A to float
+ %C = fptoui float %B to i32
+ ret i32 %C
+}
+
+; This can't fold because the 26-bit input won't fit the mantissa
+; even after disarding the signed bit.
+; CHECK-LABEL: test17
+; CHECK: sitofp
+; CHECK-NEXT: fptoui
+define i32 @test17(i26 %A) nounwind {
+ %B = sitofp i26 %A to float
+ %C = fptoui float %B to i32
+ ret i32 %C
+}
+
+; This can fold because the 54-bit output is signed and we disard the sign bit.
+; CHECK-LABEL: test18
+; CHECK: trunc
+define i54 @test18(i64 %A) nounwind {
+ %B = sitofp i64 %A to double
+ %C = fptosi double %B to i54
+ ret i54 %C
+}
+
+; This can't fold because the 55-bit output won't fit the mantissa
+; even after disarding the sign bit.
+; CHECK-LABEL: test19
+; CHECK: sitofp
+; CHECK-NEXT: fptosi
+define i55 @test19(i64 %A) nounwind {
+ %B = sitofp i64 %A to double
+ %C = fptosi double %B to i55
+ ret i55 %C
+}
+