[llvm] [Analysis] Treat ldexpf() as missing on MinGW (PR #84748)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Martin Storsjö (mstorsjo)

<details>
<summary>Changes</summary>

The function does exist, but it is a plain wrapper over regular ldexp(), so there's no benefit in calling it over regular ldexp(). Therefore, treat it as missing.

This fixes builds of Wine for aarch64 with Clang in mingw mode, which regressed recently in 8d976c7f20fe8d92fe6f54af411594e15fac25ae, as Wine uses such compilers without the regular mingw support libraries. (However, if the transformation to use ldexpf() would have made sense, the right fix would have been for Wine to provide a similar ldexpf->ldexp wrapper just like mingw does.)

---
Full diff: https://github.com/llvm/llvm-project/pull/84748.diff


2 Files Affected:

- (modified) llvm/lib/Analysis/TargetLibraryInfo.cpp (+5) 
- (modified) llvm/test/Transforms/InstCombine/exp2-1.ll (+1) 


``````````diff
diff --git a/llvm/lib/Analysis/TargetLibraryInfo.cpp b/llvm/lib/Analysis/TargetLibraryInfo.cpp
index 835268bb2d8528..c8195584ade378 100644
--- a/llvm/lib/Analysis/TargetLibraryInfo.cpp
+++ b/llvm/lib/Analysis/TargetLibraryInfo.cpp
@@ -456,6 +456,11 @@ static void initialize(TargetLibraryInfoImpl &TLI, const Triple &T,
     TLI.setUnavailable(LibFunc_uname);
     TLI.setUnavailable(LibFunc_unsetenv);
     TLI.setUnavailable(LibFunc_utimes);
+
+    // MinGW does have ldexpf, but it is a plain wrapper over regular ldexp.
+    // Therefore it's not beneficial to transform code to use it, i.e.
+    // just pretend that the function is not available.
+    TLI.setUnavailable(LibFunc_ldexpf);
   }
 
   // Pick just one set of new/delete variants.
diff --git a/llvm/test/Transforms/InstCombine/exp2-1.ll b/llvm/test/Transforms/InstCombine/exp2-1.ll
index 79aeded2fa5c3b..8419854d3ec64a 100644
--- a/llvm/test/Transforms/InstCombine/exp2-1.ll
+++ b/llvm/test/Transforms/InstCombine/exp2-1.ll
@@ -4,6 +4,7 @@
 ; RUN: opt < %s -passes=instcombine -S -mtriple=unknown | FileCheck %s -check-prefixes=LDEXP32
 ; RUN: opt < %s -passes=instcombine -S -mtriple=msp430 | FileCheck %s -check-prefixes=LDEXP16
 ; RUN: opt < %s -passes=instcombine -S -mtriple=i386-pc-win32 | FileCheck %s -check-prefixes=NOLDEXPF
+; RUN: opt < %s -passes=instcombine -S -mtriple=i386-windows-gnu | FileCheck %s -check-prefixes=NOLDEXPF
 ; RUN: opt < %s -passes=instcombine -S -mtriple=amdgcn-unknown-unknown | FileCheck %s -check-prefixes=NOLDEXP
 
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"

``````````

</details>


https://github.com/llvm/llvm-project/pull/84748