[SCCP] Infer return attributes in SCCP as well (#106732)

nikic · web-flow · commit 24fe1d4fd619 · 2024-09-02T11:44:37.000+02:00
We can infer the range/nonnull attributes in non-interprocedural SCCP as
well. The results may be better after the function has been simplified.
diff --git a/clang/test/CodeGen/attr-counted-by.c b/clang/test/CodeGen/attr-counted-by.c
@@ -639,7 +639,7 @@ void test6(struct anon_struct *p, int index) {
   p->array[index] = __builtin_dynamic_object_size(p->array, 1);
 }
 
-// SANITIZE-WITH-ATTR-LABEL: define dso_local i64 @test6_bdos(
+// SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 0, -3) i64 @test6_bdos(
 // SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[P:%.*]]) local_unnamed_addr #[[ATTR2]] {
 // SANITIZE-WITH-ATTR-NEXT:  entry:
 // SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_GEP:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 8
@@ -649,7 +649,7 @@ void test6(struct anon_struct *p, int index) {
 // SANITIZE-WITH-ATTR-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV]], i64 0, i64 [[TMP0]]
 // SANITIZE-WITH-ATTR-NEXT:    ret i64 [[TMP1]]
 //
-// NO-SANITIZE-WITH-ATTR-LABEL: define dso_local i64 @test6_bdos(
+// NO-SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 0, -3) i64 @test6_bdos(
 // NO-SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[P:%.*]]) local_unnamed_addr #[[ATTR2]] {
 // NO-SANITIZE-WITH-ATTR-NEXT:  entry:
 // NO-SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_GEP:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 8
@@ -955,7 +955,7 @@ void test10(struct union_of_fams *p, int index) {
   p->bytes[index] = (unsigned char)__builtin_dynamic_object_size(p->bytes, 1);
 }
 
-// SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 -2147483648, 2147483648) i64 @test10_bdos(
+// SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 0, 2147483648) i64 @test10_bdos(
 // SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[P:%.*]]) local_unnamed_addr #[[ATTR2]] {
 // SANITIZE-WITH-ATTR-NEXT:  entry:
 // SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_GEP:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 8
@@ -964,7 +964,7 @@ void test10(struct union_of_fams *p, int index) {
 // SANITIZE-WITH-ATTR-NEXT:    [[TMP0:%.*]] = zext nneg i32 [[NARROW]] to i64
 // SANITIZE-WITH-ATTR-NEXT:    ret i64 [[TMP0]]
 //
-// NO-SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 -2147483648, 2147483648) i64 @test10_bdos(
+// NO-SANITIZE-WITH-ATTR-LABEL: define dso_local range(i64 0, 2147483648) i64 @test10_bdos(
 // NO-SANITIZE-WITH-ATTR-SAME: ptr nocapture noundef readonly [[P:%.*]]) local_unnamed_addr #[[ATTR2]] {
 // NO-SANITIZE-WITH-ATTR-NEXT:  entry:
 // NO-SANITIZE-WITH-ATTR-NEXT:    [[DOT_COUNTED_BY_GEP:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 8
diff --git a/llvm/include/llvm/Transforms/Utils/SCCPSolver.h b/llvm/include/llvm/Transforms/Utils/SCCPSolver.h
@@ -137,7 +137,7 @@ class SCCPSolver {
   const ValueLatticeElement &getLatticeValueFor(Value *V) const;
 
   /// getTrackedRetVals - Get the inferred return value map.
-  const MapVector<Function *, ValueLatticeElement> &getTrackedRetVals();
+  const MapVector<Function *, ValueLatticeElement> &getTrackedRetVals() const;
 
   /// getTrackedGlobals - Get and return the set of inferred initializers for
   /// global variables.
@@ -190,6 +190,8 @@ class SCCPSolver {
   bool removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
                               BasicBlock *&NewUnreachableBB) const;
 
+  void inferReturnAttributes() const;
+
   bool tryToReplaceWithConstant(Value *V);
 
   // Helper to check if \p LV is either a constant or a constant
diff --git a/llvm/lib/Transforms/IPO/SCCP.cpp b/llvm/lib/Transforms/IPO/SCCP.cpp
@@ -277,34 +277,10 @@ static bool runIPSCCP(
   // whether other functions are optimizable.
   SmallVector<ReturnInst*, 8> ReturnsToZap;
 
-  for (const auto &I : Solver.getTrackedRetVals()) {
-    Function *F = I.first;
-    const ValueLatticeElement &ReturnValue = I.second;
-
-    // If there is a known constant range for the return value, add range
-    // attribute to the return value.
-    if (ReturnValue.isConstantRange() &&
-        !ReturnValue.getConstantRange().isSingleElement()) {
-      // Do not add range metadata if the return value may include undef.
-      if (ReturnValue.isConstantRangeIncludingUndef())
-        continue;
-
-      // Take the intersection of the existing attribute and the inferred range.
-      ConstantRange CR = ReturnValue.getConstantRange();
-      if (F->hasRetAttribute(Attribute::Range))
-        CR = CR.intersectWith(F->getRetAttribute(Attribute::Range).getRange());
-      F->addRangeRetAttr(CR);
-      continue;
-    }
-    // Infer nonnull return attribute.
-    if (F->getReturnType()->isPointerTy() && ReturnValue.isNotConstant() &&
-        ReturnValue.getNotConstant()->isNullValue() &&
-        !F->hasRetAttribute(Attribute::NonNull)) {
-      F->addRetAttr(Attribute::NonNull);
-      continue;
-    }
-    if (F->getReturnType()->isVoidTy())
-      continue;
+  Solver.inferReturnAttributes();
+  for (const auto &[F, ReturnValue] : Solver.getTrackedRetVals()) {
+    assert(!F->getReturnType()->isVoidTy() &&
+           "should not track void functions");
     if (SCCPSolver::isConstant(ReturnValue) || ReturnValue.isUnknownOrUndef())
       findReturnsToZap(*F, ReturnsToZap, Solver);
   }
diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Analysis/DomTreeUpdater.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/ValueLatticeUtils.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
@@ -66,6 +67,11 @@ static bool runSCCP(Function &F, const DataLayout &DL,
       DL, [TLI](Function &F) -> const TargetLibraryInfo & { return *TLI; },
       F.getContext());
 
+  // While we don't do any actual inter-procedural analysis, still track
+  // return values so we can infer attributes.
+  if (canTrackReturnsInterprocedurally(&F))
+    Solver.addTrackedFunction(&F);
+
   // Mark the first block of the function as being executable.
   Solver.markBlockExecutable(&F.front());
 
@@ -115,6 +121,8 @@ static bool runSCCP(Function &F, const DataLayout &DL,
     if (!DeadBB->hasAddressTaken())
       DTU.deleteBB(DeadBB);
 
+  Solver.inferReturnAttributes();
+
   return MadeChanges;
 }
 
diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -354,6 +354,34 @@ bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
   return true;
 }
 
+void SCCPSolver::inferReturnAttributes() const {
+  for (const auto &[F, ReturnValue] : getTrackedRetVals()) {
+
+    // If there is a known constant range for the return value, add range
+    // attribute to the return value.
+    if (ReturnValue.isConstantRange() &&
+        !ReturnValue.getConstantRange().isSingleElement()) {
+      // Do not add range metadata if the return value may include undef.
+      if (ReturnValue.isConstantRangeIncludingUndef())
+        continue;
+
+      // Take the intersection of the existing attribute and the inferred range.
+      ConstantRange CR = ReturnValue.getConstantRange();
+      if (F->hasRetAttribute(Attribute::Range))
+        CR = CR.intersectWith(F->getRetAttribute(Attribute::Range).getRange());
+      F->addRangeRetAttr(CR);
+      continue;
+    }
+    // Infer nonnull return attribute.
+    if (F->getReturnType()->isPointerTy() && ReturnValue.isNotConstant() &&
+        ReturnValue.getNotConstant()->isNullValue() &&
+        !F->hasRetAttribute(Attribute::NonNull)) {
+      F->addRetAttr(Attribute::NonNull);
+      continue;
+    }
+  }
+}
+
 /// Helper class for SCCPSolver. This implements the instruction visitor and
 /// holds all the state.
 class SCCPInstVisitor : public InstVisitor<SCCPInstVisitor> {
@@ -2168,7 +2196,7 @@ const ValueLatticeElement &SCCPSolver::getLatticeValueFor(Value *V) const {
 }
 
 const MapVector<Function *, ValueLatticeElement> &
-SCCPSolver::getTrackedRetVals() {
+SCCPSolver::getTrackedRetVals() const {
   return Visitor->getTrackedRetVals();
 }
 
diff --git a/llvm/test/Transforms/PhaseOrdering/icmp-ashr-breaking-select-idiom.ll b/llvm/test/Transforms/PhaseOrdering/icmp-ashr-breaking-select-idiom.ll
@@ -2,7 +2,7 @@
 ; RUN: opt -O1 -S < %s  | FileCheck %s
 
 define i32 @testa(i32 %mul) {
-; CHECK-LABEL: define range(i32 -65536, 65536) i32 @testa(
+; CHECK-LABEL: define range(i32 -65536, 32768) i32 @testa(
 ; CHECK-SAME: i32 [[MUL:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:    [[SHR:%.*]] = ashr i32 [[MUL]], 15
 ; CHECK-NEXT:    [[SPEC_SELECT_I:%.*]] = tail call i32 @llvm.smin.i32(i32 [[SHR]], i32 32767)
@@ -16,7 +16,7 @@ define i32 @testa(i32 %mul) {
 }
 
 define i32 @testb(i32 %mul) {
-; CHECK-LABEL: define range(i32 -16777216, 16777216) i32 @testb(
+; CHECK-LABEL: define range(i32 -128, 128) i32 @testb(
 ; CHECK-SAME: i32 [[MUL:%.*]]) local_unnamed_addr #[[ATTR0]] {
 ; CHECK-NEXT:    [[SHR102:%.*]] = ashr i32 [[MUL]], 7
 ; CHECK-NEXT:    [[TMP1:%.*]] = tail call i32 @llvm.smax.i32(i32 [[SHR102]], i32 -128)
diff --git a/llvm/test/Transforms/SCCP/exact-flags.ll b/llvm/test/Transforms/SCCP/exact-flags.ll
@@ -2,7 +2,7 @@
 ; RUN: opt -passes=sccp < %s -S | FileCheck %s
 
 define i8 @ashr_to_lshr(i8 %x, i8 %y) {
-; CHECK-LABEL: define i8 @ashr_to_lshr(
+; CHECK-LABEL: define range(i8 0, -128) i8 @ashr_to_lshr(
 ; CHECK-SAME: i8 [[X:%.*]], i8 [[Y:%.*]]) {
 ; CHECK-NEXT:    [[P:%.*]] = and i8 [[X]], 127
 ; CHECK-NEXT:    [[R:%.*]] = lshr exact i8 [[P]], [[Y]]
@@ -14,7 +14,7 @@ define i8 @ashr_to_lshr(i8 %x, i8 %y) {
 }
 
 define i8 @sdiv_to_udiv(i8 %x, i8 %y) {
-; CHECK-LABEL: define i8 @sdiv_to_udiv(
+; CHECK-LABEL: define range(i8 0, -128) i8 @sdiv_to_udiv(
 ; CHECK-SAME: i8 [[X:%.*]], i8 [[Y:%.*]]) {
 ; CHECK-NEXT:    [[X1:%.*]] = and i8 [[X]], 127
 ; CHECK-NEXT:    [[Y1:%.*]] = and i8 [[Y]], 127
diff --git a/llvm/test/Transforms/SCCP/phis.ll b/llvm/test/Transforms/SCCP/phis.ll
@@ -100,7 +100,7 @@ end:
 }
 
 define <2 x i16> @phi_vector_merge1(i1 %c, <2 x i8> %a) {
-; CHECK-LABEL: define <2 x i16> @phi_vector_merge1(
+; CHECK-LABEL: define range(i16 2, 259) <2 x i16> @phi_vector_merge1(
 ; CHECK-SAME: i1 [[C:%.*]], <2 x i8> [[A:%.*]]) {
 ; CHECK-NEXT:  [[ENTRY:.*]]:
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext <2 x i8> [[A]] to <2 x i16>
@@ -126,7 +126,7 @@ join:
 }
 
 define <2 x i16> @phi_vector_merge2(i1 %c, <2 x i8> %a) {
-; CHECK-LABEL: define <2 x i16> @phi_vector_merge2(
+; CHECK-LABEL: define range(i16 2, 259) <2 x i16> @phi_vector_merge2(
 ; CHECK-SAME: i1 [[C:%.*]], <2 x i8> [[A:%.*]]) {
 ; CHECK-NEXT:  [[ENTRY:.*]]:
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext <2 x i8> [[A]] to <2 x i16>
diff --git a/llvm/test/Transforms/SCCP/pointer-nonnull.ll b/llvm/test/Transforms/SCCP/pointer-nonnull.ll
@@ -232,13 +232,9 @@ define i1 @ip_test_nonnull_caller(ptr %p) {
 }
 
 define ptr @ret_nonnull_pointer(ptr nonnull %p) {
-; SCCP-LABEL: define ptr @ret_nonnull_pointer(
-; SCCP-SAME: ptr nonnull [[P:%.*]]) {
-; SCCP-NEXT:    ret ptr [[P]]
-;
-; IPSCCP-LABEL: define nonnull ptr @ret_nonnull_pointer(
-; IPSCCP-SAME: ptr nonnull [[P:%.*]]) {
-; IPSCCP-NEXT:    ret ptr [[P]]
+; CHECK-LABEL: define nonnull ptr @ret_nonnull_pointer(
+; CHECK-SAME: ptr nonnull [[P:%.*]]) {
+; CHECK-NEXT:    ret ptr [[P]]
 ;
   ret ptr %p
 }

Original file line number	Diff line number	Diff line change
`@@ -232,13 +232,9 @@ define i1 @ip_test_nonnull_caller(ptr %p) {`
`232`	`232`	`}`
`233`	`233`
`234`	`234`	`define ptr @ret_nonnull_pointer(ptr nonnull %p) {`
`235`		`-; SCCP-LABEL: define ptr @ret_nonnull_pointer(`
`236`		`-; SCCP-SAME: ptr nonnull [[P:%.*]]) {`
`237`		`-; SCCP-NEXT: ret ptr [[P]]`
`238`		`-;`
`239`		`-; IPSCCP-LABEL: define nonnull ptr @ret_nonnull_pointer(`
`240`		`-; IPSCCP-SAME: ptr nonnull [[P:%.*]]) {`
`241`		`-; IPSCCP-NEXT: ret ptr [[P]]`
	`235`	`+; CHECK-LABEL: define nonnull ptr @ret_nonnull_pointer(`
	`236`	`+; CHECK-SAME: ptr nonnull [[P:%.*]]) {`
	`237`	`+; CHECK-NEXT: ret ptr [[P]]`
`242`	`238`	`;`
`243`	`239`	`ret ptr %p`
`244`	`240`	`}`