[mlir] do not inject malloc/free in to-LLVM translation

[ftynse]

In the early days of MLIR-to-LLVM IR translation, it had to forcefully inject declarations of malloc and free functions as then-standard (now memref) dialect ops were unconditionally lowering to libc calls. This is no longer the case. Even when they do lower to libc calls, the signatures of those methods are injected at lowering since calls must target declared functions in valid IR. Don't inject those declarations anymore.

[llvmbot]

@llvm/pr-subscribers-mlir-llvm

@llvm/pr-subscribers-mlir

Author: Oleksandr "Alex" Zinenko (ftynse)

Changes

In the early days of MLIR-to-LLVM IR translation, it had to forcefully inject declarations of malloc and free functions as then-standard (now memref) dialect ops were unconditionally lowering to libc calls. This is no longer the case. Even when they do lower to libc calls, the signatures of those methods are injected at lowering since calls must target declared functions in valid IR. Don't inject those declarations anymore.

---

Full diff: https://github.com/llvm/llvm-project/pull/73224.diff

2 Files Affected:

• (modified) mlir/lib/Target/LLVMIR/ModuleTranslation.cpp (-8)
• (modified) mlir/test/Target/LLVMIR/llvmir.mlir (+1-1)

diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index ef1c8c21d54b08f..c5df0c7ec181a7c 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -1320,14 +1320,6 @@ prepareLLVMModule(Operation *m, llvm::LLVMContext &llvmContext,
           m->getDiscardableAttr(LLVM::LLVMDialect::getTargetTripleAttrName()))
     llvmModule->setTargetTriple(cast<StringAttr>(targetTripleAttr).getValue());
 
-  // Inject declarations for `malloc` and `free` functions that can be used in
-  // memref allocation/deallocation coming from standard ops lowering.
-  llvm::IRBuilder<> builder(llvmContext);
-  llvmModule->getOrInsertFunction("malloc", builder.getInt8PtrTy(),
-                                  builder.getInt64Ty());
-  llvmModule->getOrInsertFunction("free", builder.getVoidTy(),
-                                  builder.getInt8PtrTy());
-
   return llvmModule;
 }
 
diff --git a/mlir/test/Target/LLVMIR/llvmir.mlir b/mlir/test/Target/LLVMIR/llvmir.mlir
index 73fcee0dd2e70bd..ab8506ff163efe6 100644
--- a/mlir/test/Target/LLVMIR/llvmir.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir.mlir
@@ -179,7 +179,7 @@ llvm.mlir.global internal constant @sectionvar("teststring")  {section = ".mysec
 // CHECK: declare ptr @malloc(i64)
 llvm.func @malloc(i64) -> !llvm.ptr
 // CHECK: declare void @free(ptr)
-
+llvm.func @free(!llvm.ptr)
 
 //
 // Basic functionality: function and block conversion, function calls,

[gysit]

LGTM

[Hardcode84]

There seems to a failure in main now:

# .---command stderr------------
# | D:\projs\llvm\llvm-project\mlir\test\CAPI\translation.c:49:12: error: CHECK: expected string not found in input
# |  // CHECK: declare ptr @malloc(i64 %{{.*}})
# |            ^
# | <stdin>:1:15: note: scanning from here
# | testToLLVMIR()
# |               ^
# | <stdin>:7:2: note: possible intended match here
# |  ret i64 %3
# |  ^
# |
# | Input file: <stdin>
# | Check file: D:\projs\llvm\llvm-project\mlir\test\CAPI\translation.c
# |
# | -dump-input=help explains the following input dump.
# |
# | Input was:
# | <<<<<<
# |             1: testToLLVMIR()
# | check:49'0                   X error: no match found
# |             2: ; ModuleID = 'LLVMDialectModule'
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             3: source_filename = "LLVMDialectModule"
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             4:
# | check:49'0     ~
# |             5: define i64 @add(i64 %0, i64 %1) {
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |             6:  %3 = add i64 %0, %1
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~
# |             7:  ret i64 %3
# | check:49'0     ~~~~~~~~~~~~
# | check:49'1      ?           possible intended match
# |             8: }
# | check:49'0     ~~
# |             9:
# | check:49'0     ~
# |            10: !llvm.module.flags = !{!0}
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |            11:
# | check:49'0     ~
# |            12: !0 = !{i32 2, !"Debug Info Version", i32 3}
# | check:49'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1

Failed Tests (1):
  MLIR :: CAPI/translation.c

[ftynse]

Looks like a clash with another change that added that test.

[ftynse]

c50972d