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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.

llvm-svn: 60068
This commit is contained in:
Chris Lattner 2008-11-26 00:26:16 +00:00
parent f0e01def8c
commit a9ab165b08
3 changed files with 28 additions and 1 deletions
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11
llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
View File

@ -636,6 +636,17 @@ bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
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;

2
llvm/test/CodeGen/X86/2008-10-16-SpillerBug.ll
View File

@ -1,4 +1,4 @@
; RUN: llvm-as < %s | llc -relocation-model=pic -disable-fp-elim -mtriple=i386-apple-darwin | grep and | grep 7 | grep ebp
; RUN: llvm-as < %s | llc -relocation-model=pic -disable-fp-elim -mtriple=i386-apple-darwin | grep {andl.*7.*ecx}
%struct.XXDActiveTextureTargets = type { i64, i64, i64, i64, i64, i64 }
%struct.XXDAlphaTest = type { float, i16, i8, i8 }

16
llvm/test/CodeGen/X86/isel-sink2.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: llvm-as < %s | llc -march=x86 | grep {movzbl.7(%...)}
; RUN: llvm-as < %s | llc -march=x86 | not grep leal
define i8 @test(i32 *%P) nounwind {
%Q = getelementptr i32* %P, i32 1
%R = bitcast i32* %Q to i8*
%S = load i8* %R
%T = icmp eq i8 %S, 0
br i1 %T, label %TB, label %F
TB:
ret i8 4
F:
%U = getelementptr i8* %R, i32 3
%V = load i8* %U
ret i8 %V
}