Author: clamb
Date: Mon Dec 10 01:24:06 2007
New Revision: 44785
URL: http://llvm.org/viewvc/llvm-project?rev=44785&view=rev
Log:
Improve branch folding by recgonizing that explict successor relationships
impact the value of fall-through choices.
Modified:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
llvm/trunk/test/CodeGen/X86/2007-06-14-branchfold.ll
Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=44785&r1=44784&r2=44785&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Mon Dec 10 01:24:06 2007
@@ -775,6 +775,11 @@
// optimize branches that branch to either a return block or an assert block
// into a fallthrough to the return.
if (MBB1->empty() || MBB2->empty()) return false;
+
+ // If there is a clear successor ordering we make sure that one block
+ // will fall through to the next
+ if (MBB1->isSuccessor(MBB2)) return true;
+ if (MBB2->isSuccessor(MBB1)) return false;
MachineInstr *MBB1I = --MBB1->end();
MachineInstr *MBB2I = --MBB2->end();
Modified: llvm/trunk/test/CodeGen/X86/2007-06-14-branchfold.ll
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2007-06-14-branchfold.ll?rev=44785&r1=44784&r2=44785&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/2007-06-14-branchfold.ll (original)
+++ llvm/trunk/test/CodeGen/X86/2007-06-14-branchfold.ll Mon Dec 10 01:24:06
2007
@@ -1,7 +1,5 @@
-; RUN: llvm-as < %s | llc -mcpu=i686 | grep jmp | count 1
+; RUN: llvm-as < %s | llc -mcpu=i686 | not grep jmp
; check that branch folding understands FP_REG_KILL is not a branch
-; the remaining jmp can be removed if we take advantage of knowing
-; abort does not return
; ModuleID = 'g.bc'
target datalayout =
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64"
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