[GlobalMerge] Fix handling of const options

For the NewPM, the merge-const option was assigned to an unused
option field. Assign it to the correct one. The merge-const-aggressive
option was not supported -- and invalid options were silently ignored.
Accept it and error on invalid options.

For the LegacyPM, the corresponding cl::opt options were ignored when
called via opt rather than llc.

Author: nikic

llvm/include/llvm/CodeGen/GlobalMerge.h

@@ -25,7 +25,6 @@ struct GlobalMergeOptions {
   unsigned MinSize = 0;
   bool GroupByUse = true;
   bool IgnoreSingleUse = true;
-  bool MergeConst = false;
   /// Whether we should merge global variables that have external linkage.
   bool MergeExternal = true;
   /// Whether we should merge constant global variables.

llvm/lib/CodeGen/GlobalMerge.cpp

@@ -198,6 +198,8 @@ class GlobalMerge : public FunctionPass {
 
   explicit GlobalMerge() : FunctionPass(ID) {
     Opt.MaxOffset = GlobalMergeMaxOffset;
+    Opt.MergeConstantGlobals = EnableGlobalMergeOnConst;
+    Opt.MergeConstAggressive = GlobalMergeAllConst;
     initializeGlobalMergePass(*PassRegistry::getPassRegistry());
   }
 

llvm/lib/Passes/PassBuilder.cpp

@@ -1313,7 +1313,9 @@ Expected<GlobalMergeOptions> parseGlobalMergeOptions(StringRef Params) {
     else if (ParamName == "ignore-single-use")
       Result.IgnoreSingleUse = Enable;
     else if (ParamName == "merge-const")
-      Result.MergeConst = Enable;
+      Result.MergeConstantGlobals = Enable;
+    else if (ParamName == "merge-const-aggressive")
+      Result.MergeConstAggressive = Enable;
     else if (ParamName == "merge-external")
       Result.MergeExternal = Enable;
     else if (ParamName.consume_front("max-offset=")) {
@@ -1322,6 +1324,10 @@ Expected<GlobalMergeOptions> parseGlobalMergeOptions(StringRef Params) {
             formatv("invalid GlobalMergePass parameter '{0}' ", ParamName)
                 .str(),
             inconvertibleErrorCode());
+    } else {
+      return make_error<StringError>(
+          formatv("invalid global-merge pass parameter '{0}' ", Params).str(),
+          inconvertibleErrorCode());
     }
   }
   return Result;

llvm/lib/Passes/PassRegistry.def

@@ -178,9 +178,10 @@ MODULE_PASS_WITH_PARAMS(
     "global-merge", "GlobalMergePass",
     [TM = TM](GlobalMergeOptions Opts) { return GlobalMergePass(TM, Opts); },
     parseGlobalMergeOptions,
-    "group-by-use;ignore-single-use;max-offset=N;merge-const;merge-external;"
-    "no-group-by-use;no-ignore-single-use;no-merge-const;no-merge-external;"
-    "size-only")
+    "group-by-use;ignore-single-use;max-offset=N;merge-const;"
+    "merge-const-aggressive;merge-external;no-group-by-use;"
+    "no-ignore-single-use;no-merge-const;no-merge-const-aggressive;"
+    "no-merge-external;size-only")
 MODULE_PASS_WITH_PARAMS(
     "embed-bitcode", "EmbedBitcodePass",
     [](EmbedBitcodeOptions Opts) { return EmbedBitcodePass(Opts); },

llvm/test/Transforms/GlobalMerge/constants.ll

@@ -0,0 +1,22 @@
+; RUN: opt -global-merge -global-merge-max-offset=100 -global-merge-on-const -S < %s | FileCheck %s
+; RUN: opt -global-merge -global-merge-max-offset=100 -global-merge-on-const -global-merge-all-const -S < %s | FileCheck %s --check-prefix=AGGRESSIVE
+; RUN: opt -passes='global-merge<max-offset=100;merge-const>' -S < %s | FileCheck %s
+; RUN: opt -passes='global-merge<max-offset=100;merge-const;merge-const-aggressive>' -S < %s | FileCheck %s --check-prefix=AGGRESSIVE
+
+; CHECK: @_MergedGlobals = private constant <{ i32, i32 }> <{ i32 1, i32 2 }>, align 4
+; AGGRESSIVE: @_MergedGlobals = private constant <{ i32, i32, i32 }> <{ i32 1, i32 2, i32 3 }>, align 4
+
+@a = internal constant i32 1
+@b = internal constant i32 2
+@c = internal constant i32 3
+
+define void @use() {
+  %a = load i32, ptr @a
+  %b = load i32, ptr @b
+  ret void
+}
+
+define void @use2() {
+  %c = load i32, ptr @c
+  ret void
+}