David Majnemer 5cbd5a13a4 InstCombine: Properly optimize or'ing bittests together ... CFE, with -03, would turn: bool f(unsigned x) { bool a = x & 1; bool b = x & 2; return a | b; } into: %1 = lshr i32 %x, 1 %2 = or i32 %1, %x %3 = and i32 %2, 1 %4 = icmp ne i32 %3, 0 This sort of thing exposes a nasty pathology in GCC, ICC and LLVM. Instead, we would rather want: %1 = and i32 %x, 3 %2 = icmp ne i32 %1, 0 Things get a bit more interesting in the following case: %1 = lshr i32 %x, %y %2 = or i32 %1, %x %3 = and i32 %2, 1 %4 = icmp ne i32 %3, 0 Replacing it with the following sequence is better: %1 = shl nuw i32 1, %y %2 = or i32 %1, 1 %3 = and i32 %2, %x %4 = icmp ne i32 %3, 0 This sequence is preferable because %1 doesn't involve %x and could potentially be hoisted out of loops if it is invariant; only perform this transform in the non-constant case if we know we won't increase register pressure. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216343 91177308-0d34-0410-b5e6-96231b3b80d8		2014-08-24 09:10:57 +00:00
..
CMakeLists.txt
InstCombine.h	InstCombine: Fold ((A | B) & C1) ^ (B & C2) -> (A & C1) ^ B if C1^C2=-1	2014-08-21 05:14:48 +00:00
InstCombineAddSub.cpp	InstCombine: sub nsw %x, C -> add nsw %x, -C if C isn't INT_MIN	2014-08-22 16:41:23 +00:00
InstCombineAndOrXor.cpp	InstCombine: Fold ((A | B) & C1) ^ (B & C2) -> (A & C1) ^ B if C1^C2=-1	2014-08-21 05:14:48 +00:00
InstCombineCalls.cpp
InstCombineCasts.cpp
InstCombineCompares.cpp	InstCombine: Properly optimize or'ing bittests together	2014-08-24 09:10:57 +00:00
InstCombineLoadStoreAlloca.cpp
InstCombineMulDivRem.cpp	Remove an InstCombine that transformed patterns like (x * uitofp i1 y) to (select y, x, 0.0) when the multiply has fast math flags set.	2014-08-17 03:51:29 +00:00
InstCombinePHI.cpp	Repace SmallPtrSet with SmallPtrSetImpl in function arguments to avoid needing to mention the size.	2014-08-21 05:55:13 +00:00
InstCombineSelect.cpp
InstCombineShifts.cpp
InstCombineSimplifyDemanded.cpp	InstCombine: Don't unconditionally preserve 'nuw' when shrinking constants	2014-08-22 17:11:04 +00:00
InstCombineVectorOps.cpp
InstCombineWorklist.h	Canonicalize header guards into a common format.	2014-08-13 16:26:38 +00:00
InstructionCombining.cpp	Repace SmallPtrSet with SmallPtrSetImpl in function arguments to avoid needing to mention the size.	2014-08-21 05:55:13 +00:00
LLVMBuild.txt
Makefile