[NFC][FuncSpec] Add a test to show redundant function cloning.

[labrinea]

Summary

This happens when we find identical specializations. Despite the call site pointing to the right clone, we do emit a dead copy (compute.3 in this example).

[chill]

llvm/test/Transforms/FunctionSpecialization/identical-specializations.ll

3

Don't we avoid old PM syntax in new tests?

[labrinea]

Chages from last revision:

• used the command line option syntax of the new pass manager
• added a recursive call to demonstrate the issue found in D135463

But the same ought to happen for:

void g(int x, int y) { ... g(x, 2); ... }
...
g(1, 2);

llvm/test/Transforms/FunctionSpecialization/identical-specializations.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=function-specialization -force-function-specialization -S < %s | FileCheck %s
+
+define i64 @main(i64 %x, i64 %y, i1 %flag) {
+; CHECK-LABEL: @main(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[FLAG:%.*]], label [[PLUS:%.*]], label [[MINUS:%.*]]
+; CHECK:       plus:
+; CHECK-NEXT:    [[CMP0:%.*]] = call i64 @compute.1(i64 [[X:%.*]], i64 [[Y:%.*]], i64 (i64, i64)* @plus, i64 (i64, i64)* @minus)
+; CHECK-NEXT:    br label [[MERGE:%.*]]
+; CHECK:       minus:
+; CHECK-NEXT:    [[CMP1:%.*]] = call i64 @compute.2(i64 [[X]], i64 [[Y]], i64 (i64, i64)* @minus, i64 (i64, i64)* @plus)
+; CHECK-NEXT:    br label [[MERGE]]
+; CHECK:       merge:
+; CHECK-NEXT:    [[PH:%.*]] = phi i64 [ [[CMP0]], [[PLUS]] ], [ [[CMP1]], [[MINUS]] ]
+; CHECK-NEXT:    [[CMP2:%.*]] = call i64 @compute.1(i64 [[PH]], i64 42, i64 (i64, i64)* @plus, i64 (i64, i64)* @minus)
+; CHECK-NEXT:    ret i64 [[CMP2]]
+;
+entry:
+  br i1 %flag, label %plus, label %minus
+
+plus:
+  %cmp0 = call i64 @compute(i64 %x, i64 %y, i64 (i64, i64)* @plus, i64 (i64, i64)* @minus)
+  br label %merge
+
+minus:
+  %cmp1 = call i64 @compute(i64 %x, i64 %y, i64 (i64, i64)* @minus, i64 (i64, i64)* @plus)
+  br label %merge
+
+merge:
+  %ph = phi i64 [ %cmp0, %plus ], [ %cmp1, %minus]
+  %cmp2 = call i64 @compute(i64 %ph, i64 42, i64 (i64, i64)* @plus, i64 (i64, i64)* @minus)
+  ret i64 %cmp2
+}
+
+define internal i64 @compute(i64 %x, i64 %y, i64 (i64, i64)* %binop1, i64 (i64, i64)* %binop2) {
+entry:
+  %op0 = call i64 %binop1(i64 %x, i64 %y)
+  %op1 = call i64 %binop2(i64 %x, i64 %y)
+  %op2 = call i64 @compute(i64 %x, i64 %y, i64 (i64, i64)* %binop1, i64 (i64, i64)* @plus)
+  %add0 = add i64 %op0, %op1
+  %add1 = add i64 %add0, %op2
+  %div = sdiv i64 %add1, %x
+  %sub = sub i64 %div, %y
+  %mul = mul i64 %sub, 2
+  ret i64 %mul
+}
+
+define internal i64 @plus(i64 %x, i64 %y) {
+; CHECK-LABEL: @plus(
+entry:
+  %add = add i64 %x, %y
+  ret i64 %add
+}
+
+define internal i64 @minus(i64 %x, i64 %y) {
+; CHECK-LABEL: @minus(
+entry:
+  %sub = sub i64 %x, %y
+  ret i64 %sub
+}
+
+; CHECK-LABEL: @compute.1
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP0:%.*]] = call i64 @plus(i64 [[X:%.*]], i64 [[Y:%.*]])
+; CHECK-NEXT:    [[CMP1:%.*]] = call i64 @minus(i64 [[X]], i64 [[Y]])
+; CHECK-NEXT:    [[CMP2:%.*]] = call i64 @compute(i64 [[X]], i64 [[Y]], i64 (i64, i64)* @plus, i64 (i64, i64)* @plus)
+
+; CHECK-LABEL: @compute.2
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP0:%.*]] = call i64 @minus(i64 [[X:%.*]], i64 [[Y:%.*]])
+; CHECK-NEXT:    [[CMP1:%.*]] = call i64 @plus(i64 [[X]], i64 [[Y]])
+; CHECK-NEXT:    [[CMP2:%.*]] = call i64 @compute(i64 [[X]], i64 [[Y]], i64 (i64, i64)* @minus, i64 (i64, i64)* @plus)
+
+; CHECK-LABEL: @compute.3
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP0:%.*]] = call i64 @plus(i64 [[X:%.*]], i64 [[Y:%.*]])
+; CHECK-NEXT:    [[CMP1:%.*]] = call i64 @minus(i64 [[X]], i64 [[Y]])
+; CHECK-NEXT:    [[CMP2:%.*]] = call i64 @compute(i64 [[X]], i64 [[Y]], i64 (i64, i64)* @plus, i64 (i64, i64)* @plus)