[ARM] Fix correctness checks in promoteToConstantPool.

Correctly check for relocations in the constant to promote. And don't
allow promoting a constant multiple times.

This partially fixes https://bugs.llvm.org//show_bug.cgi?id=32780 ;
it's not a complete fix because we also need to prevent
ARMConstantIslands from cloning the constant.

(-arm-promote-constant is currently off by default, and it stays off
with this patch. I'll look into turning it on again when all the known
issues are fixed.)

Differential Revision: https://reviews.llvm.org/D51472

llvm-svn: 343361

3 files changed, 38 insertions, 62 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 15b64ef1173..bfff368a8fe 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -3072,41 +3072,8 @@ static bool allUsersAreInFunction(const Value *V, const Function *F) {
   return true;
 }
 
-/// Return true if all users of V are within some (any) function, looking through
-/// ConstantExprs. In other words, are there any global constant users?
-static bool allUsersAreInFunctions(const Value *V) {
-  SmallVector<const User*,4> Worklist;
-  for (auto *U : V->users())
-    Worklist.push_back(U);
-  while (!Worklist.empty()) {
-    auto *U = Worklist.pop_back_val();
-    if (isa<ConstantExpr>(U)) {
-      for (auto *UU : U->users())
-        Worklist.push_back(UU);
-      continue;
-    }
-
-    if (!isa<Instruction>(U))
-      return false;
-  }
-  return true;
-}
-
-// Return true if T is an integer, float or an array/vector of either.
-static bool isSimpleType(Type *T) {
-  if (T->isIntegerTy() || T->isFloatingPointTy())
-    return true;
-  Type *SubT = nullptr;
-  if (T->isArrayTy())
-    SubT = T->getArrayElementType();
-  else if (T->isVectorTy())
-    SubT = T->getVectorElementType();
-  else
-    return false;
-  return SubT->isIntegerTy() || SubT->isFloatingPointTy();
-}
-
-static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
+static SDValue promoteToConstantPool(const ARMTargetLowering *TLI,
+                                     const GlobalValue *GV, SelectionDAG &DAG,
                                      EVT PtrVT, const SDLoc &dl) {
   // If we're creating a pool entry for a constant global with unnamed address,
   // and the global is small enough, we can emit it inline into the constant pool
@@ -3133,11 +3100,11 @@ static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
       !GVar->hasLocalLinkage())
     return SDValue();
 
-  // Ensure that we don't try and inline any type that contains pointers. If
-  // we inline a value that contains relocations, we move the relocations from
-  // .data to .text which is not ideal.
+  // If we inline a value that contains relocations, we move the relocations
+  // from .data to .text. This is not allowed in position-independent code.
   auto *Init = GVar->getInitializer();
-  if (!isSimpleType(Init->getType()))
+  if ((TLI->isPositionIndependent() || TLI->getSubtarget()->isROPI()) &&
+      Init->needsRelocation())
     return SDValue();
 
   // The constant islands pass can only really deal with alignment requests
@@ -3169,12 +3136,14 @@ static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
         ConstpoolPromotionMaxTotal)
       return SDValue();
 
-  // This is only valid if all users are in a single function OR it has users
-  // in multiple functions but it no larger than a pointer. We also check if
-  // GVar has constant (non-ConstantExpr) users. If so, it essentially has its
-  // address taken.
-  if (!allUsersAreInFunction(GVar, &F) &&
-      !(Size <= 4 && allUsersAreInFunctions(GVar)))
+  // This is only valid if all users are in a single function; we can't clone
+  // the constant in general. The LLVM IR unnamed_addr allows merging
+  // constants, but not cloning them.
+  //
+  // We could potentially allow cloning if we could prove all uses of the
+  // constant in the current function don't care about the address, like
+  // printf format strings. But that isn't implemented for now.
+  if (!allUsersAreInFunction(GVar, &F))
     return SDValue();
 
   // We're going to inline this global. Pad it out if needed.
@@ -3230,7 +3199,7 @@ SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,
 
   // promoteToConstantPool only if not generating XO text section
   if (TM.shouldAssumeDSOLocal(*GV->getParent(), GV) && !Subtarget->genExecuteOnly())
-    if (SDValue V = promoteToConstantPool(GV, DAG, PtrVT, dl))
+    if (SDValue V = promoteToConstantPool(this, GV, DAG, PtrVT, dl))
       return V;
 
   if (isPositionIndependent()) {
diff --git a/llvm/test/CodeGen/ARM/constantpool-promote-dbg.ll b/llvm/test/CodeGen/ARM/constantpool-promote-dbg.ll
index bd5cb9ae060..4a6a7fe44ae 100644
--- a/llvm/test/CodeGen/ARM/constantpool-promote-dbg.ll
+++ b/llvm/test/CodeGen/ARM/constantpool-promote-dbg.ll
@@ -6,14 +6,14 @@ target triple = "thumbv7m--linux-gnu"
 @.str = private unnamed_addr constant [4 x i8] c"abc\00", align 1
 
 ; CHECK-LABEL: fn1
-; CHECK: .str:
+; CHECK: .long .L.str
 define arm_aapcscc i8* @fn1() local_unnamed_addr #0 !dbg !8 {
 entry:
   ret i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), !dbg !14
 }
 
 ; CHECK-LABEL: fn2
-; CHECK-NOT: .str:
+; CHECK: .long .L.str
 define arm_aapcscc i8* @fn2() local_unnamed_addr #0 !dbg !15 {
 entry:
   ret i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 1), !dbg !16
diff --git a/llvm/test/CodeGen/ARM/constantpool-promote.ll b/llvm/test/CodeGen/ARM/constantpool-promote.ll
index bea9c9f170c..ac16e600c14 100644
--- a/llvm/test/CodeGen/ARM/constantpool-promote.ll
+++ b/llvm/test/CodeGen/ARM/constantpool-promote.ll
@@ -1,5 +1,5 @@
-; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=static -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM
-; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=pic -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM
+; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=static -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM,CHECK-STATIC
+; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=pic -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM,CHECK-PIC
 ; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=ropi -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM
 ; RUN: llc -mtriple armv7--linux-gnueabihf -relocation-model=rwpi -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7ARM
 ; RUN: llc -mtriple thumbv7--linux-gnueabihf -relocation-model=static -arm-promote-constant < %s | FileCheck %s --check-prefixes=CHECK,CHECK-V7,CHECK-V7THUMB
@@ -16,11 +16,13 @@
 @.str2 = private unnamed_addr constant [27 x i8] c"this string is just right!\00", align 1
 @.str3 = private unnamed_addr constant [26 x i8] c"this string is used twice\00", align 1
 @.str4 = private unnamed_addr constant [29 x i8] c"same string in two functions\00", align 1
+@.str5 = private unnamed_addr constant [2 x i8] c"s\00", align 1
 @.arr1 = private unnamed_addr constant [2 x i16] [i16 3, i16 4], align 2
 @.arr2 = private unnamed_addr constant [2 x i16] [i16 7, i16 8], align 2
 @.arr3 = private unnamed_addr constant [2 x i16*] [i16* null, i16* null], align 4
 @.ptr = private unnamed_addr constant [2 x i16*] [i16* getelementptr inbounds ([2 x i16], [2 x i16]* @.arr2, i32 0, i32 0), i16* null], align 2
 @.arr4 = private unnamed_addr constant [2 x i16] [i16 3, i16 4], align 16
+@.arr5 = private unnamed_addr constant [2 x i16] [i16 3, i16 4], align 2
 @.zerosize = private unnamed_addr constant [0 x i16] zeroinitializer, align 4
 @implicit_alignment_vector = private unnamed_addr constant <4 x i32> <i32 1, i32 2, i32 3, i32 4>
 
@@ -76,20 +78,14 @@ define void @test5b() #0 {
 }
 
 ; CHECK-LABEL: @test6a
-; CHECK: adr r0, [[x:.*]]
-; CHECK: [[x]]:
-; CHECK: .short 3
-; CHECK: .short 4
+; CHECK: L.arr1
 define void @test6a() #0 {
   tail call void @c(i16* getelementptr inbounds ([2 x i16], [2 x i16]* @.arr1, i32 0, i32 0)) #2
   ret void
 }
 
 ; CHECK-LABEL: @test6b
-; CHECK: adr r0, [[x:.*]]
-; CHECK: [[x]]:
-; CHECK: .short 3
-; CHECK: .short 4
+; CHECK: L.arr1
 define void @test6b() #0 {
   tail call void @c(i16* getelementptr inbounds ([2 x i16], [2 x i16]* @.arr1, i32 0, i32 0)) #2
   ret void
@@ -103,9 +99,9 @@ define void @test7() #0 {
   ret void  
 }
 
-; This shouldn't be promoted, because the array contains pointers.
+; This can be promoted; it contains pointers, but they don't need relocations.
 ; CHECK-LABEL: @test8
-; CHECK-NOT: .zero
+; CHECK: .zero
 ; CHECK: .fnend
 define void @test8() #0 {
   %a = load i16*, i16** getelementptr inbounds ([2 x i16*], [2 x i16*]* @.arr3, i32 0, i32 0)
@@ -113,6 +109,17 @@ define void @test8() #0 {
   ret void
 }
 
+; This can't be promoted in PIC mode because it contains pointers to other globals.
+; CHECK-LABEL: @test8a
+; CHECK-STATIC: .long .L.arr2
+; CHECK-PIC: .long .L.ptr
+; CHECK: .fnend
+define void @test8a() #0 {
+  %a = load i16*, i16** getelementptr inbounds ([2 x i16*], [2 x i16*]* @.ptr, i32 0, i32 0)
+  tail call void @c(i16* %a) #2
+  ret void
+}
+
 @fn1.a = private unnamed_addr constant [4 x i16] [i16 4, i16 0, i16 0, i16 0], align 2
 @fn2.a = private unnamed_addr constant [8 x i8] [i8 4, i8 0, i8 0, i8 0, i8 23, i8 0, i8 6, i8 0], align 1
 
@@ -157,7 +164,7 @@ define void @pr32130() #0 {
 ; CHECK-V7: [[x]]:
 ; CHECK-V7: .asciz "s\000\000"
 define void @test10(i8* %a) local_unnamed_addr #0 {
-  call void @llvm.memmove.p0i8.p0i8.i32(i8* align 1 %a, i8* align 1 getelementptr inbounds ([2 x i8], [2 x i8]* @.str, i32 0, i32 0), i32 1, i1 false)
+  call void @llvm.memmove.p0i8.p0i8.i32(i8* align 1 %a, i8* align 1 getelementptr inbounds ([2 x i8], [2 x i8]* @.str5, i32 0, i32 0), i32 1, i1 false)
   ret void
 }
 
@@ -175,7 +182,7 @@ define void @test10(i8* %a) local_unnamed_addr #0 {
 ; CHECK-V7ARM: .short 3
 ; CHECK-V7ARM: .short 4
 define void @test11(i16* %a) local_unnamed_addr #0 {
-  call void @llvm.memmove.p0i16.p0i16.i32(i16* align 2 %a, i16* align 2 getelementptr inbounds ([2 x i16], [2 x i16]* @.arr1, i32 0, i32 0), i32 2, i1 false)
+  call void @llvm.memmove.p0i16.p0i16.i32(i16* align 2 %a, i16* align 2 getelementptr inbounds ([2 x i16], [2 x i16]* @.arr5, i32 0, i32 0), i32 2, i1 false)
   ret void
 }