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[InstCombine] Propagate non-null facts to call parameters

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If a parameter to a function is known non-null, use the existing parameter attributes to record that fact at the call site. This has no optimization benefit by itself - that I know of - but is an enabling change for http://reviews.llvm.org/D9129.

Differential Revision: http://reviews.llvm.org/D9132

llvm-svn: 239795
This commit is contained in:
Philip Reames 2015-06-16 00:43:54 +00:00
parent df64c4d514
commit 54716a6f5b
6 changed files with 67 additions and 3 deletions
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4
include/llvm/IR/CallSite.h
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@ -27,6 +27,7 @@
#define LLVM_IR_CALLSITE_H
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Instructions.h"
@ -150,6 +151,9 @@ public:
}
IterTy arg_end() const { return (*this)->op_end() - getArgumentEndOffset(); }
iterator_range<IterTy> args() const {
return iterator_range<IterTy>(arg_begin(), arg_end());
}
bool arg_empty() const { return arg_end() == arg_begin(); }
unsigned arg_size() const { return unsigned(arg_end() - arg_begin()); }

18
lib/Transforms/InstCombine/InstCombineCalls.cpp
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@ -1391,6 +1391,24 @@ static IntrinsicInst *FindInitTrampoline(Value *Callee) {
// visitCallSite - Improvements for call and invoke instructions.
//
Instruction *InstCombiner::visitCallSite(CallSite CS) {
// Mark any parameters that are known to be non-null with the nonnull
// attribute. This is helpful for inlining calls to functions with null
// checks on their arguments.
unsigned ArgNo = 0;
for (Value *V : CS.args()) {
if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
isKnownNonNull(V)) {
AttributeSet AS = CS.getAttributes();
AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
Attribute::NonNull);
CS.setAttributes(AS);
return CS.getInstruction();
}
ArgNo++;
}
assert(ArgNo == CS.arg_size() && "sanity check");
if (isAllocLikeFn(CS.getInstruction(), TLI))
return visitAllocSite(*CS.getInstruction());

2
test/CodeGen/NVPTX/intrin-nocapture.ll
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@ -11,7 +11,7 @@ declare i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32*)
; CHECK: @bar
define void @bar() {
%t1 = alloca i32
; CHECK: call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* %t1)
; CHECK: call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* nonnull %t1)
; CHECK-NEXT: store i32 10, i32* %t1
%t2 = call i32 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i32.p0i32(i32* %t1)
store i32 10, i32* %t1

2
test/Transforms/Inline/byval-tail-call.ll
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@ -33,7 +33,7 @@ define void @frob(i32* %x) {
; CHECK: %[[POS:.*]] = alloca i32
; CHECK: %[[VAL:.*]] = load i32, i32* %x
; CHECK: store i32 %[[VAL]], i32* %[[POS]]
; CHECK: {{^ *}}call void @ext(i32* %[[POS]]
; CHECK: {{^ *}}call void @ext(i32* nonnull %[[POS]]
; CHECK: tail call void @ext(i32* null)
; CHECK: ret void
tail call void @qux(i32* byval %x)

42
test/Transforms/InstCombine/nonnull-param.ll Normal file
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@ -0,0 +1,42 @@
; RUN: opt -S -instcombine < %s | FileCheck %s
declare void @callee(i8* %arg)
; Positive test - arg is known non null
define void @test(i8* nonnull %arg) {
; CHECK-LABEL: @test
; CHECK: call void @callee(i8* nonnull %arg)
call void @callee(i8* %arg)
ret void
}
; Negative test - arg is not known to be non null
define void @test2(i8* %arg) {
; CHECK-LABEL: @test2
; CHECK: call void @callee(i8* %arg)
call void @callee(i8* %arg)
ret void
}
declare void @callee2(i8*, i8*, i8*)
; Sanity check arg indexing
define void @test3(i8* %arg1, i8* nonnull %arg2, i8* %arg3) {
; CHECK-LABEL: @test3
; CHECK: call void @callee2(i8* %arg1, i8* nonnull %arg2, i8* %arg3)
call void @callee2(i8* %arg1, i8* %arg2, i8* %arg3)
ret void
}
; Because of the way CallSite::paramHasAttribute looks at the callee
; directly, we will not set the attribute on the CallSite. That's
; fine as long as all consumers use the same check.
define void @test4(i8* nonnull %arg) {
; CHECK-LABEL: @test4
; CHECK: call void @test4(i8* %arg)
call void @test4(i8* %arg)
ret void
}

2
test/Transforms/InstCombine/select.ll
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@ -1265,7 +1265,7 @@ define i32 @test77(i1 %flag, i32* %x) {
; load does.
; CHECK-LABEL: @test77(
; CHECK: %[[A:.*]] = alloca i32, align 1
; CHECK: call void @scribble_on_i32(i32* %[[A]])
; CHECK: call void @scribble_on_i32(i32* nonnull %[[A]])
; CHECK: store i32 0, i32* %x
; CHECK: %[[P:.*]] = select i1 %flag, i32* %[[A]], i32* %x
; CHECK: load i32, i32* %[[P]]