Remove alignment argument from memcpy/memmove/memset in favour of alignment attributes (Step 1)

Summary:
 This is a resurrection of work first proposed and discussed in Aug 2015:
   http://lists.llvm.org/pipermail/llvm-dev/2015-August/089384.html
and initially landed (but then backed out) in Nov 2015:
   http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html

 The @llvm.memcpy/memmove/memset intrinsics currently have an explicit argument
which is required to be a constant integer. It represents the alignment of the
dest (and source), and so must be the minimum of the actual alignment of the
two.

 This change is the first in a series that allows source and dest to each
have their own alignments by using the alignment attribute on their arguments.

 In this change we:
1) Remove the alignment argument.
2) Add alignment attributes to the source & dest arguments. We, temporarily,
   require that the alignments for source & dest be equal.

 For example, code which used to read:
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 100, i32 4, i1 false)
will now read
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %dest, i8* align 4 %src, i32 100, i1 false)

 Downstream users may have to update their lit tests that check for
@llvm.memcpy/memmove/memset call/declaration patterns. The following extended sed script
may help with updating the majority of your tests, but it does not catch all possible
patterns so some manual checking and updating will be required.

s~declare void @llvm\.mem(set|cpy|move)\.p([^(]*)\((.*), i32, i1\)~declare void @llvm.mem\1.p\2(\3, i1)~g
s~call void @llvm\.memset\.p([^(]*)i8\(i8([^*]*)\* (.*), i8 (.*), i8 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.memset.p\1i8(i8\2* \3, i8 \4, i8 \5, i1 \6)~g
s~call void @llvm\.memset\.p([^(]*)i16\(i8([^*]*)\* (.*), i8 (.*), i16 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.memset.p\1i16(i8\2* \3, i8 \4, i16 \5, i1 \6)~g
s~call void @llvm\.memset\.p([^(]*)i32\(i8([^*]*)\* (.*), i8 (.*), i32 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.memset.p\1i32(i8\2* \3, i8 \4, i32 \5, i1 \6)~g
s~call void @llvm\.memset\.p([^(]*)i64\(i8([^*]*)\* (.*), i8 (.*), i64 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.memset.p\1i64(i8\2* \3, i8 \4, i64 \5, i1 \6)~g
s~call void @llvm\.memset\.p([^(]*)i128\(i8([^*]*)\* (.*), i8 (.*), i128 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.memset.p\1i128(i8\2* \3, i8 \4, i128 \5, i1 \6)~g
s~call void @llvm\.memset\.p([^(]*)i8\(i8([^*]*)\* (.*), i8 (.*), i8 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.memset.p\1i8(i8\2* align \6 \3, i8 \4, i8 \5, i1 \7)~g
s~call void @llvm\.memset\.p([^(]*)i16\(i8([^*]*)\* (.*), i8 (.*), i16 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.memset.p\1i16(i8\2* align \6 \3, i8 \4, i16 \5, i1 \7)~g
s~call void @llvm\.memset\.p([^(]*)i32\(i8([^*]*)\* (.*), i8 (.*), i32 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.memset.p\1i32(i8\2* align \6 \3, i8 \4, i32 \5, i1 \7)~g
s~call void @llvm\.memset\.p([^(]*)i64\(i8([^*]*)\* (.*), i8 (.*), i64 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.memset.p\1i64(i8\2* align \6 \3, i8 \4, i64 \5, i1 \7)~g
s~call void @llvm\.memset\.p([^(]*)i128\(i8([^*]*)\* (.*), i8 (.*), i128 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.memset.p\1i128(i8\2* align \6 \3, i8 \4, i128 \5, i1 \7)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i8\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i8 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.mem\1.p\2i8(i8\3* \4, i8\5* \6, i8 \7, i1 \8)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i16\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i16 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.mem\1.p\2i16(i8\3* \4, i8\5* \6, i16 \7, i1 \8)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i32\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i32 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.mem\1.p\2i32(i8\3* \4, i8\5* \6, i32 \7, i1 \8)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i64\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i64 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.mem\1.p\2i64(i8\3* \4, i8\5* \6, i64 \7, i1 \8)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i128\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i128 (.*), i32 [01], i1 ([^)]*)\)~call void @llvm.mem\1.p\2i128(i8\3* \4, i8\5* \6, i128 \7, i1 \8)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i8\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i8 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.mem\1.p\2i8(i8\3* align \8 \4, i8\5* align \8 \6, i8 \7, i1 \9)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i16\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i16 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.mem\1.p\2i16(i8\3* align \8 \4, i8\5* align \8 \6, i16 \7, i1 \9)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i32\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i32 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.mem\1.p\2i32(i8\3* align \8 \4, i8\5* align \8 \6, i32 \7, i1 \9)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i64\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i64 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.mem\1.p\2i64(i8\3* align \8 \4, i8\5* align \8 \6, i64 \7, i1 \9)~g
s~call void @llvm\.mem(cpy|move)\.p([^(]*)i128\(i8([^*]*)\* (.*), i8([^*]*)\* (.*), i128 (.*), i32 ([0-9]*), i1 ([^)]*)\)~call void @llvm.mem\1.p\2i128(i8\3* align \8 \4, i8\5* align \8 \6, i128 \7, i1 \9)~g

 The remaining changes in the series will:
Step 2) Expand the IRBuilder API to allow creation of memcpy/memmove with differing
   source and dest alignments.
Step 3) Update Clang to use the new IRBuilder API.
Step 4) Update Polly to use the new IRBuilder API.
Step 5) Update LLVM passes that create memcpy/memmove calls to use the new IRBuilder API,
        and those that use use MemIntrinsicInst::[get|set]Alignment() to use
        getDestAlignment() and getSourceAlignment() instead.
Step 6) Remove the single-alignment IRBuilder API for memcpy/memmove, and the
        MemIntrinsicInst::[get|set]Alignment() methods.

Reviewers: pete, hfinkel, lhames, reames, bollu

Reviewed By: reames

Subscribers: niosHD, reames, jholewinski, qcolombet, jfb, sanjoy, arsenm, dschuff, dylanmckay, mehdi_amini, sdardis, nemanjai, david2050, nhaehnle, javed.absar, sbc100, jgravelle-google, eraman, aheejin, kbarton, JDevlieghere, asb, rbar, johnrusso, simoncook, jordy.potman.lists, apazos, sabuasal, llvm-commits

Differential Revision: https://reviews.llvm.org/D41675

llvm-svn: 322965

1 files changed, 67 insertions, 3 deletions

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index bf96e772394..5d219995aed 100644
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -22,6 +22,7 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instruction.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Verifier.h"
@@ -522,6 +523,37 @@ static bool UpgradeIntrinsicFunction1(Function *F, Function *&NewFn) {
         return true;
       }
     }
+    // Updating the memory intrinsics (memcpy/memmove/memset) that have an
+    // alignment parameter to embedding the alignment as an attribute of
+    // the pointer args.
+    if (Name.startswith("memcpy.") && F->arg_size() == 5) {
+      rename(F);
+      // Get the types of dest, src, and len
+      ArrayRef<Type *> ParamTypes = F->getFunctionType()->params().slice(0, 3);
+      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::memcpy,
+                                        ParamTypes);
+      return true;
+    }
+    if (Name.startswith("memmove.") && F->arg_size() == 5) {
+      rename(F);
+      // Get the types of dest, src, and len
+      ArrayRef<Type *> ParamTypes = F->getFunctionType()->params().slice(0, 3);
+      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::memmove,
+                                        ParamTypes);
+      return true;
+    }
+    if (Name.startswith("memset.") && F->arg_size() == 5) {
+      rename(F);
+      // Get the types of dest, and len
+      const auto *FT = F->getFunctionType();
+      Type *ParamTypes[2] = {
+          FT->getParamType(0), // Dest
+          FT->getParamType(2)  // len
+      };
+      NewFn = Intrinsic::getDeclaration(F->getParent(), Intrinsic::memset,
+                                        ParamTypes);
+      return true;
+    }
     break;
   }
   case 'n': {
@@ -2198,14 +2230,17 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
     return;
   }
 
-  CallInst *NewCall = nullptr;
-  switch (NewFn->getIntrinsicID()) {
-  default: {
+  const auto &DefaultCase = [&NewFn, &CI]() -> void {
     // Handle generic mangling change, but nothing else
     assert(
         (CI->getCalledFunction()->getName() != NewFn->getName()) &&
         "Unknown function for CallInst upgrade and isn't just a name change");
     CI->setCalledFunction(NewFn);
+  };
+  CallInst *NewCall = nullptr;
+  switch (NewFn->getIntrinsicID()) {
+  default: {
+    DefaultCase();
     return;
   }
 
@@ -2346,6 +2381,35 @@ void llvm::UpgradeIntrinsicCall(CallInst *CI, Function *NewFn) {
     NewCall = Builder.CreateCall(NewFn, Args);
     break;
   }
+
+  case Intrinsic::memcpy:
+  case Intrinsic::memmove:
+  case Intrinsic::memset: {
+    // We have to make sure that the call signature is what we're expecting.
+    // We only want to change the old signatures by removing the alignment arg:
+    //  @llvm.mem[cpy|move]...(i8*, i8*, i[32|i64], i32, i1)
+    //    -> @llvm.mem[cpy|move]...(i8*, i8*, i[32|i64], i1)
+    //  @llvm.memset...(i8*, i8, i[32|64], i32, i1)
+    //    -> @llvm.memset...(i8*, i8, i[32|64], i1)
+    // Note: i8*'s in the above can be any pointer type
+    if (CI->getNumArgOperands() != 5) {
+      DefaultCase();
+      return;
+    }
+    // Remove alignment argument (3), and add alignment attributes to the
+    // dest/src pointers.
+    Value *Args[4] = {CI->getArgOperand(0), CI->getArgOperand(1),
+                      CI->getArgOperand(2), CI->getArgOperand(4)};
+    NewCall = Builder.CreateCall(NewFn, Args);
+    auto *MemCI = cast<MemIntrinsic>(NewCall);
+    // All mem intrinsics support dest alignment.
+    const ConstantInt *Align = cast<ConstantInt>(CI->getArgOperand(3));
+    MemCI->setDestAlignment(Align->getZExtValue());
+    // Memcpy/Memmove also support source alignment.
+    if (auto *MTI = dyn_cast<MemTransferInst>(MemCI))
+      MTI->setSourceAlignment(Align->getZExtValue());
+    break;
+  }
   }
   assert(NewCall && "Should have either set this variable or returned through "
                     "the default case");