[PATCH] D104365: [FuncSpec] Enabling specializing direct constant

[Chuanqi Xu via Phabricator via llvm-commits]

ChuanqiXu updated this revision to Diff 354850.
ChuanqiXu added a comment.

Add an option to control the behavior.

Then I did some statistics for SPEC2017int

The total number of specialized functions increased about 18% (from 49 to 58)

Then I didn't find significant compile-time change with turning option on.

I wonder if this means that we can turn this option on by default.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D104365/new/

https://reviews.llvm.org/D104365

Files:
  llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
  llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-integers.ll


Index: llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-integers.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-integers.ll
@@ -0,0 +1,44 @@
+; RUN: opt -function-specialization -function-specialization-for-literal-constant=true -S < %s | FileCheck %s
+
+; Check that the direct constant parameter could be specialized.
+; CHECK: @foo.1(
+; CHECK: @foo.2(
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+
+declare i32 @getValue()
+declare i1 @getCond()
+
+define internal i32 @foo(i1 %break_cond) {
+entry:
+  br label %loop.entry
+
+loop.entry:
+  br label %loop2.entry
+
+loop2.entry:
+  br label %loop2.body
+
+loop2.body:
+  %value = call i32 @getValue()
+  br i1 %break_cond, label %loop2.end, label %return
+
+loop2.end:
+  %cond.end = call i1 @getCond()
+  br i1 %cond.end, label %loop2.entry, label %loop.end
+
+loop.end:
+  %cond2.end = call i1 @getCond()
+  br i1 %cond2.end, label %loop.entry, label %return
+
+return:
+  ret i32 %value
+}
+
+define dso_local i32 @bar(i32 %x, i32 %y) {
+entry:
+  %retval.1 = call i32 @foo(i1 1)
+  %retval.2 = call i32 @foo(i1 0)
+  %retval = add nsw i32 %retval.1, %retval.2
+  ret i32 %retval
+}
\ No newline at end of file
Index: llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -64,6 +64,10 @@
                           cl::desc("Average loop iteration count cost"),
                           cl::init(10));
 
+static cl::opt<bool> EnableSpecializeForLiteralConstant(
+  "function-specialization-for-literal-constant", cl::init(false), cl::Hidden,
+  cl::desc("Make function specialization available for literal constant."));
+
 // Helper to check if \p LV is either overdefined or a constant int.
 static bool isOverdefined(const ValueLatticeElement &LV) {
   return !LV.isUnknownOrUndef() && !LV.isConstant();
@@ -471,17 +475,11 @@
         }
       }
 
-      // Get the lattice value for the value the call site passes to the
-      // argument. If this value is not constant, move on to the next call
-      // site. Additionally, set the AllConstant flag to false.
-      if (V != A && !Solver.getLatticeValueFor(V).isConstant()) {
+      if (isa<Constant>(V) && (Solver.getLatticeValueFor(V).isConstant() || 
+                               EnableSpecializeForLiteralConstant))
+        Constants.push_back(cast<Constant>(V));
+      else
         AllConstant = false;
-        continue;
-      }
-
-      // Add the constant to the set.
-      if (auto *C = dyn_cast<Constant>(CS.getArgOperand(A->getArgNo())))
-        Constants.push_back(C);
     }
 
     // If the argument can only take on constant values, AllConstant will be


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