Add CallSiteSplitting pass
Summary:
This change add a pass which tries to split a call-site to pass
more constrained arguments if its argument is predicated in the control flow
so that we can expose better context to the later passes (e.g, inliner, jump
threading, or IPA-CP based function cloning, etc.).
As of now we support two cases :
1) If a call site is dominated by an OR condition and if any of its arguments
are predicated on this OR condition, try to split the condition with more
constrained arguments. For example, in the code below, we try to split the
call site since we can predicate the argument (ptr) based on the OR condition.
Split from :
if (!ptr || c)
callee(ptr);
to :
if (!ptr)
callee(null ptr) // set the known constant value
else if (c)
callee(nonnull ptr) // set non-null attribute in the argument
2) We can also split a call-site based on constant incoming values of a PHI
For example,
from :
BB0:
%c = icmp eq i32 %i1, %i2
br i1 %c, label %BB2, label %BB1
BB1:
br label %BB2
BB2:
%p = phi i32 [ 0, %BB0 ], [ 1, %BB1 ]
call void @bar(i32 %p)
to
BB0:
%c = icmp eq i32 %i1, %i2
br i1 %c, label %BB2-split0, label %BB1
BB1:
br label %BB2-split1
BB2-split0:
call void @bar(i32 0)
br label %BB2
BB2-split1:
call void @bar(i32 1)
br label %BB2
BB2:
%p = phi i32 [ 0, %BB2-split0 ], [ 1, %BB2-split1 ]
Reviewers: davidxl, huntergr, chandlerc, mcrosier, eraman, davide
Reviewed By: davidxl
Subscribers: sdesmalen, ashutosh.nema, fhahn, mssimpso, aemerson, mgorny, mehdi_amini, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D39137
llvm-svn: 317351
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 21d95a0..2088ea0 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -89,6 +89,7 @@
#include "llvm/Transforms/Scalar/ADCE.h"
#include "llvm/Transforms/Scalar/AlignmentFromAssumptions.h"
#include "llvm/Transforms/Scalar/BDCE.h"
+#include "llvm/Transforms/Scalar/CallSiteSplitting.h"
#include "llvm/Transforms/Scalar/ConstantHoisting.h"
#include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
#include "llvm/Transforms/Scalar/DCE.h"
@@ -548,6 +549,9 @@
EarlyFPM.addPass(SROA());
EarlyFPM.addPass(EarlyCSEPass());
EarlyFPM.addPass(LowerExpectIntrinsicPass());
+ if (Level == O3)
+ EarlyFPM.addPass(CallSiteSplittingPass());
+
// In SamplePGO ThinLTO backend, we need instcombine before profile annotation
// to convert bitcast to direct calls so that they can be inlined during the
// profile annotation prepration step.
@@ -920,13 +924,16 @@
MPM.addPass(InferFunctionAttrsPass());
if (Level > 1) {
+ FunctionPassManager EarlyFPM(DebugLogging);
+ EarlyFPM.addPass(CallSiteSplittingPass());
+ MPM.addPass(createModuleToFunctionPassAdaptor(std::move(EarlyFPM)));
+
// Indirect call promotion. This should promote all the targets that are
// left by the earlier promotion pass that promotes intra-module targets.
// This two-step promotion is to save the compile time. For LTO, it should
// produce the same result as if we only do promotion here.
MPM.addPass(PGOIndirectCallPromotion(
true /* InLTO */, PGOOpt && !PGOOpt->SampleProfileFile.empty()));
-
// Propagate constants at call sites into the functions they call. This
// opens opportunities for globalopt (and inlining) by substituting function
// pointers passed as arguments to direct uses of functions.