[IR] Use Min behavior for module flag "PIC Level"

Using Max for both "PIC Level" and "PIE Level" is inconsistent. PIC imposes less
restriction while PIE imposes more restriction. The result generally
picks the more restrictive behavior: Min for PIC.

This choice matches `ld -r`: a non-pic object and a pic object merge into a
result which should be treated as non-pic.

To allow linking "PIC Level" using Error/Max from old bitcode files, upgrade
Error/Max to Min.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D130531

13 files changed, 52 insertions, 34 deletions

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index 75594f9..18ea2fd 100644
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -4391,26 +4391,34 @@ bool llvm::UpgradeModuleFlags(Module &M) {
     MDString *ID = dyn_cast_or_null<MDString>(Op->getOperand(1));
     if (!ID)
       continue;
+    auto SetBehavior = [&](Module::ModFlagBehavior B) {
+      Metadata *Ops[3] = {ConstantAsMetadata::get(ConstantInt::get(
+                              Type::getInt32Ty(M.getContext()), B)),
+                          MDString::get(M.getContext(), ID->getString()),
+                          Op->getOperand(2)};
+      ModFlags->setOperand(I, MDNode::get(M.getContext(), Ops));
+      Changed = true;
+    };
+
     if (ID->getString() == "Objective-C Image Info Version")
       HasObjCFlag = true;
     if (ID->getString() == "Objective-C Class Properties")
       HasClassProperties = true;
-    // Upgrade PIC/PIE Module Flags. The module flag behavior for these two
-    // field was Error and now they are Max.
-    if (ID->getString() == "PIC Level" || ID->getString() == "PIE Level") {
+    // Upgrade PIC from Error/Max to Min.
+    if (ID->getString() == "PIC Level") {
       if (auto *Behavior =
               mdconst::dyn_extract_or_null<ConstantInt>(Op->getOperand(0))) {
-        if (Behavior->getLimitedValue() == Module::Error) {
-          Type *Int32Ty = Type::getInt32Ty(M.getContext());
-          Metadata *Ops[3] = {
-              ConstantAsMetadata::get(ConstantInt::get(Int32Ty, Module::Max)),
-              MDString::get(M.getContext(), ID->getString()),
-              Op->getOperand(2)};
-          ModFlags->setOperand(I, MDNode::get(M.getContext(), Ops));
-          Changed = true;
-        }
+        uint64_t V = Behavior->getLimitedValue();
+        if (V == Module::Error || V == Module::Max)
+          SetBehavior(Module::Min);
       }
     }
+    // Upgrade "PIE Level" from Error to Max.
+    if (ID->getString() == "PIE Level")
+      if (auto *Behavior =
+              mdconst::dyn_extract_or_null<ConstantInt>(Op->getOperand(0)))
+        if (Behavior->getLimitedValue() == Module::Error)
+          SetBehavior(Module::Max);
 
     // Upgrade branch protection and return address signing module flags. The
     // module flag behavior for these fields were Error and now they are Min.
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index b51ea45..5dd114c 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -596,7 +596,9 @@ PICLevel::Level Module::getPICLevel() const {
 }
 
 void Module::setPICLevel(PICLevel::Level PL) {
-  addModuleFlag(ModFlagBehavior::Max, "PIC Level", PL);
+  // The merge result of a non-PIC object and a PIC object can only be reliably
+  // used as a non-PIC object, so use the Min merge behavior.
+  addModuleFlag(ModFlagBehavior::Min, "PIC Level", PL);
 }
 
 PIELevel::Level Module::getPIELevel() const {
diff --git a/llvm/test/Bitcode/upgrade-module-flag.ll b/llvm/test/Bitcode/upgrade-module-flag.ll
index 539265be..1004fd8 100644
--- a/llvm/test/Bitcode/upgrade-module-flag.ll
+++ b/llvm/test/Bitcode/upgrade-module-flag.ll
@@ -8,7 +8,7 @@
 !2 = !{i32 1, !"Objective-C Image Info Version", i32 0}
 !3 = !{i32 1, !"Objective-C Image Info Section", !"__DATA, __objc_imageinfo, regular, no_dead_strip"}
 
-; CHECK: !0 = !{i32 7, !"PIC Level", i32 1}
+; CHECK: !0 = !{i32 8, !"PIC Level", i32 1}
 ; CHECK: !1 = !{i32 7, !"PIE Level", i32 1}
 ; CHECK: !2 = !{i32 1, !"Objective-C Image Info Version", i32 0}
 ; CHECK: !3 = !{i32 1, !"Objective-C Image Info Section", !"__DATA,__objc_imageinfo,regular,no_dead_strip"}
diff --git a/llvm/test/Bitcode/upgrade-pic-level.ll b/llvm/test/Bitcode/upgrade-pic-level.ll
new file mode 100644
index 0000000..55bd2d8
--- /dev/null
+++ b/llvm/test/Bitcode/upgrade-pic-level.ll
@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+; RUN: verify-uselistorder < %s
+
+!llvm.module.flags = !{!0}
+
+; CHECK: !0 = !{i32 8, !"PIC Level", i32 1}
+
+!0 = !{i32 7, !"PIC Level", i32 1}
diff --git a/llvm/test/Linker/Inputs/module-flags-pic-2-b.ll b/llvm/test/Linker/Inputs/module-flags-pic-2-b.ll
index f652edd..f84a1ec 100644
--- a/llvm/test/Linker/Inputs/module-flags-pic-2-b.ll
+++ b/llvm/test/Linker/Inputs/module-flags-pic-2-b.ll
@@ -1,4 +1,4 @@
-!0 = !{ i32 7, !"PIC Level", i32 2 }
+!0 = !{ i32 8, !"PIC Level", i32 2 }
 !1 = !{ i32 7, !"PIE Level", i32 2 }
 
 !llvm.module.flags = !{!0, !1}
diff --git a/llvm/test/Linker/module-flags-pic-1-a.ll b/llvm/test/Linker/module-flags-pic-1-a.ll
index 9074aa6..6a05a71 100644
--- a/llvm/test/Linker/module-flags-pic-1-a.ll
+++ b/llvm/test/Linker/module-flags-pic-1-a.ll
@@ -6,4 +6,4 @@
 
 !llvm.module.flags = !{!0}
 ; CHECK: !llvm.module.flags = !{!0}
-; CHECK: !0 = !{i32 7, !"PIC Level", i32 1}
+; CHECK: !0 = !{i32 8, !"PIC Level", i32 1}
diff --git a/llvm/test/Linker/module-flags-pic-2-a.ll b/llvm/test/Linker/module-flags-pic-2-a.ll
index 8898d72..ac67437 100644
--- a/llvm/test/Linker/module-flags-pic-2-a.ll
+++ b/llvm/test/Linker/module-flags-pic-2-a.ll
@@ -2,10 +2,10 @@
 
 ; test linking modules with two different PIC and PIE levels
 
-!0 = !{ i32 7, !"PIC Level", i32 1 }
+!0 = !{ i32 8, !"PIC Level", i32 1 }
 !1 = !{ i32 7, !"PIE Level", i32 1 }
 
 !llvm.module.flags = !{!0, !1}
 
-; CHECK: !0 = !{i32 7, !"PIC Level", i32 2}
+; CHECK: !0 = !{i32 8, !"PIC Level", i32 1}
 ; CHECK: !1 = !{i32 7, !"PIE Level", i32 2}
diff --git a/llvm/test/Transforms/Attributor/value-simplify-dbg.ll b/llvm/test/Transforms/Attributor/value-simplify-dbg.ll
index 527677d..cf41d10 100644
--- a/llvm/test/Transforms/Attributor/value-simplify-dbg.ll
+++ b/llvm/test/Transforms/Attributor/value-simplify-dbg.ll
@@ -58,7 +58,7 @@ declare i32 @speculatable() speculatable readnone
 !7 = !{i32 7, !"Dwarf Version", i32 5}
 !8 = !{i32 2, !"Debug Info Version", i32 3}
 !9 = !{i32 1, !"wchar_size", i32 4}
-!10 = !{i32 7, !"PIC Level", i32 2}
+!10 = !{i32 8, !"PIC Level", i32 2}
 !11 = !{i32 7, !"PIE Level", i32 2}
 !12 = !{i32 7, !"uwtable", i32 2}
 !13 = !{i32 7, !"frame-pointer", i32 2}
@@ -88,7 +88,7 @@ declare i32 @speculatable() speculatable readnone
 ; CHECK: [[META7:![0-9]+]] = !{i32 7, !"Dwarf Version", i32 5}
 ; CHECK: [[META8:![0-9]+]] = !{i32 2, !"Debug Info Version", i32 3}
 ; CHECK: [[META9:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
-; CHECK: [[META10:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK: [[META10:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK: [[META11:![0-9]+]] = !{i32 7, !"PIE Level", i32 2}
 ; CHECK: [[META12:![0-9]+]] = !{i32 7, !"uwtable", i32 2}
 ; CHECK: [[META13:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
diff --git a/llvm/test/Transforms/Attributor/value-simplify-local-remote.ll b/llvm/test/Transforms/Attributor/value-simplify-local-remote.ll
index ec0e6c5..3a67f0c 100644
--- a/llvm/test/Transforms/Attributor/value-simplify-local-remote.ll
+++ b/llvm/test/Transforms/Attributor/value-simplify-local-remote.ll
@@ -769,7 +769,7 @@ entry:
 !1 = !{i32 1, !"wchar_size", i32 4}
 !2 = !{i32 7, !"openmp", i32 50}
 !3 = !{i32 7, !"openmp-device", i32 50}
-!4 = !{i32 7, !"PIC Level", i32 2}
+!4 = !{i32 8, !"PIC Level", i32 2}
 !5 = !{i32 7, !"frame-pointer", i32 2}
 !6 = !{i32 7, !"Dwarf Version", i32 2}
 !7 = !{i32 2, !"Debug Info Version", i32 3}
@@ -795,7 +795,7 @@ entry:
 ; CHECK: [[META1:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; CHECK: [[META2:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; CHECK: [[META3:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; CHECK: [[META4:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK: [[META4:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK: [[META5:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; CHECK: [[META6:![0-9]+]] = !{i32 7, !"Dwarf Version", i32 2}
 ; CHECK: [[META7:![0-9]+]] = !{i32 2, !"Debug Info Version", i32 3}
diff --git a/llvm/test/Transforms/OpenMP/spmdization.ll b/llvm/test/Transforms/OpenMP/spmdization.ll
index d6f7c7d..5f45d62 100644
--- a/llvm/test/Transforms/OpenMP/spmdization.ll
+++ b/llvm/test/Transforms/OpenMP/spmdization.ll
@@ -2395,7 +2395,7 @@ attributes #11 = { convergent }
 !12 = !{i32 1, !"wchar_size", i32 4}
 !13 = !{i32 7, !"openmp", i32 50}
 !14 = !{i32 7, !"openmp-device", i32 50}
-!15 = !{i32 7, !"PIC Level", i32 2}
+!15 = !{i32 8, !"PIC Level", i32 2}
 !16 = !{i32 7, !"frame-pointer", i32 2}
 !17 = !{!"clang version 14.0.0"}
 !18 = !{!19, !19, i64 0}
@@ -2481,7 +2481,7 @@ attributes #11 = { convergent }
 ; AMDGPU: [[META12:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; AMDGPU: [[META13:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; AMDGPU: [[META14:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; AMDGPU: [[META15:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; AMDGPU: [[META15:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; AMDGPU: [[META16:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; AMDGPU: [[META17:![0-9]+]] = !{!"clang version 14.0.0"}
 ; AMDGPU: [[TBAA18]] = !{!19, !19, i64 0}
@@ -2515,7 +2515,7 @@ attributes #11 = { convergent }
 ; NVPTX: [[META12:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; NVPTX: [[META13:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; NVPTX: [[META14:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; NVPTX: [[META15:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; NVPTX: [[META15:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; NVPTX: [[META16:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; NVPTX: [[META17:![0-9]+]] = !{!"clang version 14.0.0"}
 ; NVPTX: [[TBAA18]] = !{!19, !19, i64 0}
@@ -2549,7 +2549,7 @@ attributes #11 = { convergent }
 ; AMDGPU-DISABLED: [[META12:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; AMDGPU-DISABLED: [[META13:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; AMDGPU-DISABLED: [[META14:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; AMDGPU-DISABLED: [[META15:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; AMDGPU-DISABLED: [[META15:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; AMDGPU-DISABLED: [[META16:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; AMDGPU-DISABLED: [[META17:![0-9]+]] = !{!"clang version 14.0.0"}
 ; AMDGPU-DISABLED: [[TBAA18]] = !{!19, !19, i64 0}
@@ -2583,7 +2583,7 @@ attributes #11 = { convergent }
 ; NVPTX-DISABLED: [[META12:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; NVPTX-DISABLED: [[META13:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; NVPTX-DISABLED: [[META14:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; NVPTX-DISABLED: [[META15:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; NVPTX-DISABLED: [[META15:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; NVPTX-DISABLED: [[META16:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; NVPTX-DISABLED: [[META17:![0-9]+]] = !{!"clang version 14.0.0"}
 ; NVPTX-DISABLED: [[TBAA18]] = !{!19, !19, i64 0}
diff --git a/llvm/test/Transforms/OpenMP/spmdization_assumes.ll b/llvm/test/Transforms/OpenMP/spmdization_assumes.ll
index 93065a2..6c7fcd3 100644
--- a/llvm/test/Transforms/OpenMP/spmdization_assumes.ll
+++ b/llvm/test/Transforms/OpenMP/spmdization_assumes.ll
@@ -137,7 +137,7 @@ attributes #6 = { convergent nounwind "llvm.assume"="ompx_spmd_amenable" }
 !2 = !{i32 1, !"wchar_size", i32 4}
 !3 = !{i32 7, !"openmp", i32 50}
 !4 = !{i32 7, !"openmp-device", i32 50}
-!5 = !{i32 7, !"PIC Level", i32 2}
+!5 = !{i32 8, !"PIC Level", i32 2}
 !6 = !{i32 7, !"frame-pointer", i32 2}
 !7 = !{!"clang version 14.0.0"}
 !8 = !{!9, !9, i64 0}
@@ -159,7 +159,7 @@ attributes #6 = { convergent nounwind "llvm.assume"="ompx_spmd_amenable" }
 ; CHECK: [[META2:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; CHECK: [[META3:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; CHECK: [[META4:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; CHECK: [[META5:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK: [[META5:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK: [[META6:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; CHECK: [[META7:![0-9]+]] = !{!"clang version 14.0.0"}
 ; CHECK: [[TBAA8]] = !{!9, !9, i64 0}
diff --git a/llvm/test/Transforms/OpenMP/spmdization_guarding.ll b/llvm/test/Transforms/OpenMP/spmdization_guarding.ll
index e8922ab..4eb6347 100644
--- a/llvm/test/Transforms/OpenMP/spmdization_guarding.ll
+++ b/llvm/test/Transforms/OpenMP/spmdization_guarding.ll
@@ -381,7 +381,7 @@ attributes #5 = { convergent nounwind "llvm.assume"="omp_no_openmp,ompx_spmd_ame
 !2 = !{i32 1, !"wchar_size", i32 4}
 !3 = !{i32 7, !"openmp", i32 50}
 !4 = !{i32 7, !"openmp-device", i32 50}
-!5 = !{i32 7, !"PIC Level", i32 2}
+!5 = !{i32 8, !"PIC Level", i32 2}
 !6 = !{i32 7, !"frame-pointer", i32 2}
 !7 = !{!"clang version 14.0.0"}
 !8 = !{!9}
@@ -419,7 +419,7 @@ attributes #5 = { convergent nounwind "llvm.assume"="omp_no_openmp,ompx_spmd_ame
 ; CHECK: [[META2:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; CHECK: [[META3:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; CHECK: [[META4:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; CHECK: [[META5:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK: [[META5:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK: [[META6:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; CHECK: [[META7:![0-9]+]] = !{!"clang version 14.0.0"}
 ; CHECK: [[META8:![0-9]+]] = !{!9}
@@ -433,7 +433,7 @@ attributes #5 = { convergent nounwind "llvm.assume"="omp_no_openmp,ompx_spmd_ame
 ; CHECK-DISABLED: [[META2:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; CHECK-DISABLED: [[META3:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; CHECK-DISABLED: [[META4:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; CHECK-DISABLED: [[META5:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK-DISABLED: [[META5:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK-DISABLED: [[META6:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; CHECK-DISABLED: [[META7:![0-9]+]] = !{!"clang version 14.0.0"}
 ; CHECK-DISABLED: [[META8:![0-9]+]] = !{!9}
diff --git a/llvm/test/Transforms/OpenMP/spmdization_guarding_two_reaching_kernels.ll b/llvm/test/Transforms/OpenMP/spmdization_guarding_two_reaching_kernels.ll
index f56c885..c94528c 100644
--- a/llvm/test/Transforms/OpenMP/spmdization_guarding_two_reaching_kernels.ll
+++ b/llvm/test/Transforms/OpenMP/spmdization_guarding_two_reaching_kernels.ll
@@ -265,7 +265,7 @@ attributes #5 = { convergent }
 !4 = !{i32 1, !"wchar_size", i32 4}
 !5 = !{i32 7, !"openmp", i32 50}
 !6 = !{i32 7, !"openmp-device", i32 50}
-!7 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{i32 8, !"PIC Level", i32 2}
 !8 = !{i32 7, !"frame-pointer", i32 2}
 !9 = !{!"clang version 14.0.0"}
 ;.
@@ -285,7 +285,7 @@ attributes #5 = { convergent }
 ; CHECK: [[META4:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 ; CHECK: [[META5:![0-9]+]] = !{i32 7, !"openmp", i32 50}
 ; CHECK: [[META6:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
-; CHECK: [[META7:![0-9]+]] = !{i32 7, !"PIC Level", i32 2}
+; CHECK: [[META7:![0-9]+]] = !{i32 8, !"PIC Level", i32 2}
 ; CHECK: [[META8:![0-9]+]] = !{i32 7, !"frame-pointer", i32 2}
 ; CHECK: [[META9:![0-9]+]] = !{!"clang version 14.0.0"}
 ;.