[llvm-branch-commits] [llvm] 65fd034 - [FunctionAttrs] Infer willreturn for functions without loops
Nikita Popov via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Jan 21 11:48:15 PST 2021
Author: Nikita Popov
Date: 2021-01-21T20:29:33+01:00
New Revision: 65fd034b95d69fa0e634861ee165b502ceb92a12
URL: https://github.com/llvm/llvm-project/commit/65fd034b95d69fa0e634861ee165b502ceb92a12
DIFF: https://github.com/llvm/llvm-project/commit/65fd034b95d69fa0e634861ee165b502ceb92a12.diff
LOG: [FunctionAttrs] Infer willreturn for functions without loops
If a function doesn't contain loops and does not call non-willreturn
functions, then it is willreturn. Loops are detected by checking
for backedges in the function. We don't attempt to handle finite
loops at this point.
Differential Revision: https://reviews.llvm.org/D94633
Added:
Modified:
clang/test/CodeGenOpenCL/convergent.cl
llvm/lib/Transforms/IPO/FunctionAttrs.cpp
llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
llvm/test/CodeGen/AMDGPU/inline-attr.ll
llvm/test/Transforms/FunctionAttrs/atomic.ll
llvm/test/Transforms/FunctionAttrs/incompatible_fn_attrs.ll
llvm/test/Transforms/FunctionAttrs/nofree.ll
llvm/test/Transforms/FunctionAttrs/optnone.ll
llvm/test/Transforms/FunctionAttrs/willreturn.ll
llvm/test/Transforms/FunctionAttrs/writeonly.ll
llvm/test/Transforms/InferFunctionAttrs/norecurse_debug.ll
Removed:
################################################################################
diff --git a/clang/test/CodeGenOpenCL/convergent.cl b/clang/test/CodeGenOpenCL/convergent.cl
index 5e4f6fad1b3a..25951a64c114 100644
--- a/clang/test/CodeGenOpenCL/convergent.cl
+++ b/clang/test/CodeGenOpenCL/convergent.cl
@@ -134,7 +134,7 @@ kernel void assume_convergent_asm()
__asm__ volatile("s_barrier");
}
-// CHECK: attributes #0 = { nofree noinline norecurse nounwind "
+// CHECK: attributes #0 = { nofree noinline norecurse nounwind willreturn "
// CHECK: attributes #1 = { {{[^}]*}}convergent{{[^}]*}} }
// CHECK: attributes #2 = { {{[^}]*}}convergent{{[^}]*}} }
// CHECK: attributes #3 = { {{[^}]*}}convergent noduplicate{{[^}]*}} }
diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 210186a0550e..30a1f81ad0e1 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -22,6 +22,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/CGSCCPassManager.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CallGraphSCCPass.h"
@@ -1425,12 +1426,36 @@ static bool addNoReturnAttrs(const SCCNodeSet &SCCNodes) {
return Changed;
}
+static bool functionWillReturn(const Function &F) {
+ // Must-progress function without side-effects must return.
+ if (F.mustProgress() && F.onlyReadsMemory())
+ return true;
+
+ // Can only analyze functions with a definition.
+ if (F.isDeclaration())
+ return false;
+
+ // Functions with loops require more sophisticated analysis, as the loop
+ // may be infinite. For now, don't try to handle them.
+ SmallVector<std::pair<const BasicBlock *, const BasicBlock *>> Backedges;
+ FindFunctionBackedges(F, Backedges);
+ if (!Backedges.empty())
+ return false;
+
+ // If there are no loops, then the function is willreturn if all calls in
+ // it are willreturn.
+ return all_of(instructions(F), [](const Instruction &I) {
+ const auto *CB = dyn_cast<CallBase>(&I);
+ return !CB || CB->hasFnAttr(Attribute::WillReturn);
+ });
+}
+
// Set the willreturn function attribute if possible.
static bool addWillReturn(const SCCNodeSet &SCCNodes) {
bool Changed = false;
for (Function *F : SCCNodes) {
- if (!F || !F->onlyReadsMemory() || !F->mustProgress() || F->willReturn())
+ if (!F || F->willReturn() || !functionWillReturn(*F))
continue;
F->setWillReturn();
diff --git a/llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll b/llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
index 95ac2525b4ad..5bbc86bb69ed 100644
--- a/llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
+++ b/llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
@@ -72,13 +72,13 @@ define i32 @test3_no(i8* %p) nounwind {
declare void @callee(i32* %p) nounwind
declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i1) nounwind
-; CHECK: attributes #0 = { norecurse nounwind readnone }
-; CHECK: attributes #1 = { nofree norecurse nounwind writeonly }
+; CHECK: attributes #0 = { norecurse nounwind readnone willreturn }
+; CHECK: attributes #1 = { nofree norecurse nounwind willreturn writeonly }
; CHECK: attributes #2 = { nounwind readonly }
; CHECK: attributes #3 = { nounwind }
-; CHECK: attributes #4 = { nounwind readnone }
-; CHECK: attributes #5 = { nofree nounwind }
-; CHECK: attributes #6 = { nofree norecurse nounwind }
+; CHECK: attributes #4 = { nounwind readnone willreturn }
+; CHECK: attributes #5 = { nofree nounwind willreturn }
+; CHECK: attributes #6 = { nofree norecurse nounwind willreturn }
; CHECK: attributes #7 = { argmemonly nofree nosync nounwind willreturn }
; Root note.
diff --git a/llvm/test/CodeGen/AMDGPU/inline-attr.ll b/llvm/test/CodeGen/AMDGPU/inline-attr.ll
index c73a3c52e9ae..8192c4837b4b 100644
--- a/llvm/test/CodeGen/AMDGPU/inline-attr.ll
+++ b/llvm/test/CodeGen/AMDGPU/inline-attr.ll
@@ -6,14 +6,14 @@
; GCN: define amdgpu_kernel void @caller(float addrspace(1)* nocapture %p) local_unnamed_addr #1 {
; GCN: %mul.i = fmul float %load, 1.500000e+01
-; UNSAFE: attributes #0 = { norecurse nounwind readnone "unsafe-fp-math"="true" }
-; UNSAFE: attributes #1 = { nofree norecurse nounwind "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="true" }
+; UNSAFE: attributes #0 = { norecurse nounwind readnone willreturn "unsafe-fp-math"="true" }
+; UNSAFE: attributes #1 = { nofree norecurse nounwind willreturn "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="true" }
-; NOINFS: attributes #0 = { norecurse nounwind readnone "no-infs-fp-math"="true" }
-; NOINFS: attributes #1 = { nofree norecurse nounwind "less-precise-fpmad"="false" "no-infs-fp-math"="true" "no-nans-fp-math"="false" "unsafe-fp-math"="false" }
+; NOINFS: attributes #0 = { norecurse nounwind readnone willreturn "no-infs-fp-math"="true" }
+; NOINFS: attributes #1 = { nofree norecurse nounwind willreturn "less-precise-fpmad"="false" "no-infs-fp-math"="true" "no-nans-fp-math"="false" "unsafe-fp-math"="false" }
-; NONANS: attributes #0 = { norecurse nounwind readnone "no-nans-fp-math"="true" }
-; NONANS: attributes #1 = { nofree norecurse nounwind "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="true" "unsafe-fp-math"="false" }
+; NONANS: attributes #0 = { norecurse nounwind readnone willreturn "no-nans-fp-math"="true" }
+; NONANS: attributes #1 = { nofree norecurse nounwind willreturn "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="true" "unsafe-fp-math"="false" }
define float @foo(float %x) #0 {
entry:
diff --git a/llvm/test/Transforms/FunctionAttrs/atomic.ll b/llvm/test/Transforms/FunctionAttrs/atomic.ll
index 8112996404a5..313c54b5ed3e 100644
--- a/llvm/test/Transforms/FunctionAttrs/atomic.ll
+++ b/llvm/test/Transforms/FunctionAttrs/atomic.ll
@@ -20,5 +20,5 @@ entry:
ret i32 %r
}
-; CHECK: attributes #0 = { norecurse nounwind readnone ssp uwtable }
-; CHECK: attributes #1 = { nofree norecurse nounwind ssp uwtable }
+; CHECK: attributes #0 = { norecurse nounwind readnone ssp uwtable willreturn }
+; CHECK: attributes #1 = { nofree norecurse nounwind ssp uwtable willreturn }
diff --git a/llvm/test/Transforms/FunctionAttrs/incompatible_fn_attrs.ll b/llvm/test/Transforms/FunctionAttrs/incompatible_fn_attrs.ll
index 906ae01422c1..4701de3f2e54 100644
--- a/llvm/test/Transforms/FunctionAttrs/incompatible_fn_attrs.ll
+++ b/llvm/test/Transforms/FunctionAttrs/incompatible_fn_attrs.ll
@@ -28,5 +28,5 @@ entry:
attributes #0 = { argmemonly }
attributes #1 = { inaccessiblememonly }
attributes #2 = { inaccessiblemem_or_argmemonly }
-; CHECK: attributes #0 = { norecurse nounwind readnone }
+; CHECK: attributes #0 = { norecurse nounwind readnone willreturn }
; CHECK-NOT: attributes
diff --git a/llvm/test/Transforms/FunctionAttrs/nofree.ll b/llvm/test/Transforms/FunctionAttrs/nofree.ll
index 4d36cc82bae2..bcb97b34c6cc 100644
--- a/llvm/test/Transforms/FunctionAttrs/nofree.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nofree.ll
@@ -107,7 +107,7 @@ attributes #5 = { builtin nounwind }
; CHECK: attributes #0 = { uwtable }
; CHECK: attributes #1 = { nounwind uwtable }
; CHECK: attributes #2 = { nounwind }
-; CHECK: attributes #3 = { norecurse nounwind readonly uwtable }
+; CHECK: attributes #3 = { norecurse nounwind readonly uwtable willreturn }
; CHECK: attributes #4 = { nobuiltin nounwind }
; CHECK: attributes #5 = { builtin nounwind }
diff --git a/llvm/test/Transforms/FunctionAttrs/optnone.ll b/llvm/test/Transforms/FunctionAttrs/optnone.ll
index b7e9ea3636c3..9455a2ae40a0 100644
--- a/llvm/test/Transforms/FunctionAttrs/optnone.ll
+++ b/llvm/test/Transforms/FunctionAttrs/optnone.ll
@@ -20,6 +20,6 @@ declare i8 @strlen(i8*) noinline optnone
; CHECK: (i8*) #1
; CHECK-LABEL: attributes #0
-; CHECK: = { norecurse nounwind readnone }
+; CHECK: = { norecurse nounwind readnone willreturn }
; CHECK-LABEL: attributes #1
; CHECK: = { noinline optnone }
diff --git a/llvm/test/Transforms/FunctionAttrs/willreturn.ll b/llvm/test/Transforms/FunctionAttrs/willreturn.ll
index 78233769b45e..1f69c3d80d8b 100644
--- a/llvm/test/Transforms/FunctionAttrs/willreturn.ll
+++ b/llvm/test/Transforms/FunctionAttrs/willreturn.ll
@@ -71,9 +71,10 @@ B:
ret i64 0
}
+; Function without loops or non-willreturn calls will return.
define void @willreturn_no_loop(i1 %c, i32* %p) {
-; CHECK-NOT: Function Attrs: {{.*}}willreturn
-; CHECK: define void @willreturn_no_loop(
+; CHECK: Function Attrs: willreturn
+; CHECK-NEXT: define void @willreturn_no_loop(
;
br i1 %c, label %if, label %else
@@ -90,6 +91,7 @@ end:
ret void
}
+; Calls a function that is not guaranteed to return, not willreturn.
define void @willreturn_non_returning_function(i1 %c, i32* %p) {
; CHECK-NOT: Function Attrs: {{.*}}willreturn
; CHECK: define void @willreturn_non_returning_function(
@@ -98,6 +100,7 @@ define void @willreturn_non_returning_function(i1 %c, i32* %p) {
ret void
}
+; Infinite loop without mustprogress, will not return.
define void @willreturn_loop() {
; CHECK-NOT: Function Attrs: {{.*}}willreturn
; CHECK: define void @willreturn_loop(
@@ -108,6 +111,8 @@ loop:
br label %loop
}
+; Finite loop. Could be willreturn but not detected.
+; FIXME
define void @willreturn_finite_loop() {
; CHECK-NOT: Function Attrs: {{.*}}willreturn
; CHECK: define void @willreturn_finite_loop(
@@ -125,5 +130,28 @@ end:
ret void
}
+; Infinite recursion without mustprogress, will not return.
+define void @willreturn_recursion() {
+; CHECK-NOT: Function Attrs: {{.*}}willreturn
+; CHECK: define void @willreturn_recursion(
+;
+ tail call void @willreturn_recursion()
+ ret void
+}
+
+; Irreducible infinite loop, will not return.
+define void @willreturn_irreducible(i1 %c) {
+; CHECK-NOT: Function Attrs: {{.*}}willreturn
+; CHECK: define void @willreturn_irreducible(
+;
+ br i1 %c, label %bb1, label %bb2
+
+bb1:
+ br label %bb2
+
+bb2:
+ br label %bb1
+}
+
declare i64 @fn_noread() readnone
declare void @fn_willreturn() willreturn
diff --git a/llvm/test/Transforms/FunctionAttrs/writeonly.ll b/llvm/test/Transforms/FunctionAttrs/writeonly.ll
index 9be998787466..1efea78ba1e3 100644
--- a/llvm/test/Transforms/FunctionAttrs/writeonly.ll
+++ b/llvm/test/Transforms/FunctionAttrs/writeonly.ll
@@ -25,6 +25,6 @@ nouses-argworn-funwo_entry:
ret void
}
-; CHECK: attributes #0 = { {{.*}} readnone }
-; CHECK: attributes #1 = { {{.*}} readonly }
+; CHECK: attributes #0 = { {{.*}} readnone {{.*}} }
+; CHECK: attributes #1 = { {{.*}} readonly {{.*}} }
; CHECK: attributes #2 = { {{.*}} writeonly }
diff --git a/llvm/test/Transforms/InferFunctionAttrs/norecurse_debug.ll b/llvm/test/Transforms/InferFunctionAttrs/norecurse_debug.ll
index 5e284fe10be8..1afd97e44e9d 100644
--- a/llvm/test/Transforms/InferFunctionAttrs/norecurse_debug.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/norecurse_debug.ll
@@ -52,5 +52,5 @@ attributes #1 = { nounwind readnone speculatable }
!28 = !DILocation(line: 9, column: 18, scope: !2)
!29 = !DILocation(line: 10, column: 1, scope: !2)
-; CHECK: attributes #0 = { nofree norecurse nounwind }
+; CHECK: attributes #0 = { nofree norecurse nounwind willreturn }
; CHECK-NOT: foo.coefficient1
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