Fix X86's isTruncateFree to not claim that truncate to i1 is free. This fixes Bill's testcase that failed for r48491.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48542 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 1588b49..ceda932 100644
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -1647,47 +1647,3 @@
if it commuted the addl in LBB1_1.
//===---------------------------------------------------------------------===//
-
-These two functions perform identical operations:
-
-define i32 @test(i32 %f12) {
- %tmp7.25 = lshr i32 %f12, 16
- %tmp7.26 = trunc i32 %tmp7.25 to i8
- %tmp78.2 = sext i8 %tmp7.26 to i32
- ret i32 %tmp78.2
-}
-
-define i32 @test2(i32 %f12) {
- %f11 = shl i32 %f12, 8
- %tmp7.25 = ashr i32 %f11, 24
- ret i32 %tmp7.25
-}
-
-but the first compiles into significantly better code on x86-32:
-
-_test:
- movsbl 6(%esp), %eax
- ret
-_test2:
- movl 4(%esp), %eax
- shll $8, %eax
- sarl $24, %eax
- ret
-
-and on x86-64:
-
-_test:
- shrl $16, %edi
- movsbl %dil, %eax
- ret
-_test2:
- shll $8, %edi
- movl %edi, %eax
- sarl $24, %eax
- ret
-
-I would like instcombine to canonicalize the first into the second (since it is
-shorter and doesn't involve type width changes) but the x86 backend needs to do
-the right thing with the later sequence first.
-
-//===---------------------------------------------------------------------===//
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 5a05aba..93fb802 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5662,7 +5662,7 @@
return false;
unsigned NumBits1 = Ty1->getPrimitiveSizeInBits();
unsigned NumBits2 = Ty2->getPrimitiveSizeInBits();
- if (NumBits1 <= NumBits2)
+ if (NumBits1 <= NumBits2 || NumBits2 < 8)
return false;
return Subtarget->is64Bit() || NumBits1 < 64;
}
@@ -5673,7 +5673,7 @@
return false;
unsigned NumBits1 = MVT::getSizeInBits(VT1);
unsigned NumBits2 = MVT::getSizeInBits(VT2);
- if (NumBits1 <= NumBits2)
+ if (NumBits1 <= NumBits2 || NumBits2 < 8)
return false;
return Subtarget->is64Bit() || NumBits1 < 64;
}