RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-22 18:54:02 +01:00
Code Issues Projects Releases Wiki Activity

[LICM] Hoist assumes out of loops

Browse Source 
If we have an assume which is known to execute and whose operand is invariant, we can lift that into the pre-header. So long as we don't change which paths the assume executes on, this is a legal transformation. It's likely to be a useful canonicalization as other transforms only look for dominating assumes.

Differential Revision: https://reviews.llvm.org/D50364

llvm-svn: 339481
This commit is contained in:
Philip Reames 2018-08-10 22:21:56 +00:00
parent 2498063d31
commit 12e7461f52
2 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
lib/Transforms/Scalar/LICM.cpp
View File

@ -658,6 +658,15 @@ bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
if (CI->mayThrow()) if (CI->mayThrow())
return false; return false;
if (Function *F = CI->getCalledFunction())
switch (F->getIntrinsicID()) {
default: break;
// TODO: support invariant.start, and experimental.guard here
case Intrinsic::assume:
// Assumes don't actually alias anything or throw
return true;
};
// Handle simple cases by querying alias analysis. // Handle simple cases by querying alias analysis.
FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI); FunctionModRefBehavior Behavior = AA->getModRefBehavior(CI);
if (Behavior == FMRB_DoesNotAccessMemory) if (Behavior == FMRB_DoesNotAccessMemory)

2
test/Transforms/LICM/assume.ll
View File

@ -36,9 +36,9 @@ for.end104:
define void @f_1(i1 %cond, i32* %ptr) { define void @f_1(i1 %cond, i32* %ptr) {
; CHECK-LABEL: @f_1( ; CHECK-LABEL: @f_1(
; CHECK-LABEL: entry: ; CHECK-LABEL: entry:
; CHECK: call void @llvm.assume(i1 %cond)
; CHECK: %val = load i32, i32* %ptr ; CHECK: %val = load i32, i32* %ptr
; CHECK-LABEL: loop: ; CHECK-LABEL: loop:
; CHECK: call void @llvm.assume(i1 %cond)
entry: entry:
br label %loop br label %loop