Teach CodeGenPrepare to look through Bitcast instructions when attempting to
optimize addressing modes. This allows us to optimize things like isel-sink2.ll
into:
movl 4(%esp), %eax
cmpb $0, 4(%eax)
jne LBB1_2 ## F
LBB1_1: ## TB
movl $4, %eax
ret
LBB1_2: ## F
movzbl 7(%eax), %eax
ret
instead of:
_test:
movl 4(%esp), %eax
cmpb $0, 4(%eax)
leal 4(%eax), %eax
jne LBB1_2 ## F
LBB1_1: ## TB
movl $4, %eax
ret
LBB1_2: ## F
movzbl 3(%eax), %eax
ret
This shrinks (e.g.) 403.gcc from 1133510 to 1128345 lines of .s.
Note that the 2008-10-16-SpillerBug.ll testcase is dubious at best, I doubt
it is really testing what it thinks it is.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60068 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 4ba8091..0306b06 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -636,6 +636,17 @@
TLI.getPointerTy())
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
+ case Instruction::BitCast:
+ // BitCast is always a noop, and we can handle it as long as it is
+ // int->int or pointer->pointer (we don't want int<->fp or something).
+ if ((isa<PointerType>(AddrInst->getOperand(0)->getType()) ||
+ isa<IntegerType>(AddrInst->getOperand(0)->getType())) &&
+ // Don't touch identity bitcasts. These were probably put here by LSR,
+ // and we don't want to mess around with them. Assume it knows what it
+ // is doing.
+ AddrInst->getOperand(0)->getType() != AddrInst->getType())
+ return MatchAddr(AddrInst->getOperand(0), Depth);
+ return false;
case Instruction::Add: {
// Check to see if we can merge in the RHS then the LHS. If so, we win.
ExtAddrMode BackupAddrMode = AddrMode;