[ThinLTO] Ensure the TargetLibraryInfo is constructed early enough

[tejohnson]

Summary

Without this change, the WholeProgramDevirt pass, which requires the
TargetLibraryInfo, will construct one from the default triple.

Fixes PR38139.

[tejohnson]

ping

[dexonsmith]

LGTM.

lib/Transforms/IPO/PassManagerBuilder.cpp

void PassManagerBuilder::addLateLTOOptimizationPasses(
   // currently it damages debug info.
   if (MergeFunctions)
     PM.add(createMergeFunctionsPass());
 }
 
 void PassManagerBuilder::populateThinLTOPassManager(
     legacy::PassManagerBase &PM) {
   PerformThinLTO = true;
+  if (LibraryInfo)
+    PM.add(new TargetLibraryInfoWrapperPass(*LibraryInfo));
 
   if (VerifyInput)
     PM.add(createVerifierPass());
 
   if (ImportSummary) {
     // These passes import type identifier resolutions for whole-program
     // devirtualization and CFI. They must run early because other passes may
     // disturb the specific instruction patterns that these passes look for,

test/LTO/X86/triple-init.ll

+; Test to ensure that the LTO pipelines add pass to build the TargetLibraryInfo
+; using the specified target triple.
+
+; Check with regular LTO
 ; RUN: llvm-as < %s >%t1
 ; RUN: llvm-lto -exported-symbol=_main  -o %t2 %t1
-; RUN: llvm-nm %t2 | FileCheck %s 
+; RUN: llvm-nm %t2 | FileCheck %s
+; Check with ThinLTO. Use llvm-lto2 since this adds earlier passes requiring
+; the TargetLibraryInfo with ThinLTO (WholeProgramDevirt).
+; RUN: opt -module-summary -o %t1 %s
+; RUN: llvm-lto2 run -r %t1,_pow, -r %t1,_main,plx -o %t2 %t1
+; RUN: llvm-nm %t2.1 | FileCheck %s
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.9"
 
 declare double @pow(double, double)
 
 define double @main(double %x) {
 ; We check that LTO will be aware of target triple and apply pow to __exp10 transformation.
 ; CHECK: U ___exp10
   %retval = call double @pow(double 10.0, double %x)
   ret double %retval
 }

test/LTO/X86/triple-init2.ll

+; Test to ensure that the LTO pipelines add pass to build the TargetLibraryInfo
+; using the specified target triple.
+
+; Check with regular LTO
+; RUN: llvm-as < %s >%t1
+; RUN: llvm-lto -exported-symbol=main -o %t2 %t1
+; RUN: llvm-nm %t2 | FileCheck %s
+; Check with ThinLTO. Use llvm-lto2 since this adds earlier passes requiring
+; the TargetLibraryInfo with ThinLTO (WholeProgramDevirt).
+; RUN: opt -module-summary -o %t1 %s
+; RUN: llvm-lto2 run -r %t1,main,plx -o %t2 %t1
+; RUN: llvm-nm %t2.1 | FileCheck %s
+
+; We check that LTO will be aware of target triple and prevent exp2 to ldexpf
+; transformation on Windows.
+; CHECK: U exp2f
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.11.0"
+
+define dso_local i32 @main(i32 %argc, i8** nocapture readnone %argv) local_unnamed_addr {
+entry:
+  %conv = sitofp i32 %argc to float
+  %exp2 = tail call float @llvm.exp2.f32(float %conv)
+  %conv1 = fptosi float %exp2 to i32
+  ret i32 %conv1
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare float @llvm.exp2.f32(float)
+