Mark type test intrinsics as speculatable to fix inline cost

[tejohnson]

Summary

There is already code in InlineCost.cpp to identify and ignore ephemeral
values (llvm.assume intrinsics and other side-effect free instructions
only feeding the assumes). However, because llvm.type.test intrinsics
were not marked speculatable, they and any instructions specifically
feeding the type test (typically a bitcast) were being counted towards
the instruction cost when inlining. This was causing profile matching
issues in some cases when enabling -fwhole-program-vtables for whole
program devirtualization.

According to the language reference, the speculatable attribute means:
"the function does not have any effects besides calculating its result
and does not have undefined behavior". I see no reason why type tests
cannot be marked with this attribute.

There are 2 test changes:

llvm/test/Transforms/Inline/ephemeral.ll: I added a type test intrinsic
here to verify the fix. Also, I found the test was not actually testing
what it originally intended. Many of the existing instructions were
optimized away by -Oz, and the cost of inlining was negative due to the
benefit of removing the call. So I changed the test to simply invoke the
inline pass and check the number of instructions computed by InlineCost.
I also fixed an instruction that was not actually used anywhere.

llvm/test/Transforms/SimplifyCFG/no-md-sink.ll needed to be made more
robust to code changes that reordered the metadata.

[jdoerfert]

LG

[davezarzycki]

I have an auto bisecting cron job that has twice identified this change as the source of a regression when building release (no asserts). Is the following expected or can we get a quick fix?

FAIL: LLVM :: Transforms/Inline/ephemeral.ll (57376 of 76078)
******************** TEST 'LLVM :: Transforms/Inline/ephemeral.ll' FAILED ********************
Script:
--
: 'RUN: at line 1';   /tmp/_update_lc/r/bin/opt -S -inline /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll -debug-only=inline-cost 2>&1 | /tmp/_update_lc/r/bin/FileCheck /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll
--
Exit Code: 1

Command Output (stderr):
--
/home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll:4:10: error: CHECK: expected string not found in input
; CHECK: NumInstructions: 2
         ^
<stdin>:1:1: note: scanning from here
opt: Unknown command line argument '-debug-only=inline-cost'. Try: '/tmp/_update_lc/r/bin/opt --help'
^
<stdin>:2:33: note: possible intended match here
opt: Did you mean '--debug-pass=inline-cost'?
                                ^

Input file: <stdin>
Check file: /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           1: opt: Unknown command line argument '-debug-only=inline-cost'. Try: '/tmp/_update_lc/r/bin/opt --help'
check:4'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
           2: opt: Did you mean '--debug-pass=inline-cost'?
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
check:4'1                                     ?              possible intended match
>>>>>>

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
********************
Failed Tests (1):
  LLVM :: Transforms/Inline/ephemeral.ll

[tejohnson]

In D101180#2713678, @davezarzycki wrote:

I have an auto bisecting cron job that has twice identified this change as the source of a regression when building release (no asserts). Is the following expected or can we get a quick fix?

Ah, this test now uses a debug flag so needs to require asserts. Should be fixed in 38959c4624345d7e6b7d726d87c79c083298b189.

FAIL: LLVM :: Transforms/Inline/ephemeral.ll (57376 of 76078)
******************** TEST 'LLVM :: Transforms/Inline/ephemeral.ll' FAILED ********************
Script:
--
: 'RUN: at line 1';   /tmp/_update_lc/r/bin/opt -S -inline /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll -debug-only=inline-cost 2>&1 | /tmp/_update_lc/r/bin/FileCheck /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll
--
Exit Code: 1

Command Output (stderr):
--
/home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll:4:10: error: CHECK: expected string not found in input
; CHECK: NumInstructions: 2
         ^
<stdin>:1:1: note: scanning from here
opt: Unknown command line argument '-debug-only=inline-cost'. Try: '/tmp/_update_lc/r/bin/opt --help'
^
<stdin>:2:33: note: possible intended match here
opt: Did you mean '--debug-pass=inline-cost'?
                                ^

Input file: <stdin>
Check file: /home/dave/ro_s/lp/llvm/test/Transforms/Inline/ephemeral.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           1: opt: Unknown command line argument '-debug-only=inline-cost'. Try: '/tmp/_update_lc/r/bin/opt --help'
check:4'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
           2: opt: Did you mean '--debug-pass=inline-cost'?
check:4'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
check:4'1                                     ?              possible intended match
>>>>>>

--

********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
********************
Failed Tests (1):
  LLVM :: Transforms/Inline/ephemeral.ll

llvm/include/llvm/IR/Intrinsics.td

 def int_masked_compressstore:
   DefaultAttrsIntrinsic<[],
             [llvm_anyvector_ty, LLVMPointerToElt<0>,
              LLVMScalarOrSameVectorWidth<0, llvm_i1_ty>],
             [IntrWriteMem, IntrArgMemOnly, IntrWillReturn]>;
 
 // Test whether a pointer is associated with a type metadata identifier.
 def int_type_test : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_ptr_ty, llvm_metadata_ty],
-                              [IntrNoMem, IntrWillReturn]>;
+                              [IntrNoMem, IntrWillReturn, IntrSpeculatable]>;
 
 // Safely loads a function pointer from a virtual table pointer using type metadata.
 def int_type_checked_load : DefaultAttrsIntrinsic<[llvm_ptr_ty, llvm_i1_ty],
                                       [llvm_ptr_ty, llvm_i32_ty, llvm_metadata_ty],
                                       [IntrNoMem, IntrWillReturn]>;
 
 // Create a branch funnel that implements an indirect call to a limited set of
 // callees. This needs to be a musttail call.

llvm/test/Transforms/Inline/ephemeral.ll

-; RUN: opt -S -Oz %s | FileCheck %s
+; RUN: opt -S -inline %s -debug-only=inline-cost 2>&1 | FileCheck %s
+; Only the load and ret should be included in the instruction count, not
+; the instructions feeding the assume.
+; CHECK: NumInstructions: 2
 
 @a = global i32 4
 
-define i32 @inner() {
+define i32 @inner(i8* %y) {
   %a1 = load volatile i32, i32* @a
 
-  ; Here are enough instructions to prevent inlining, but because they are used
-  ; only by the @llvm.assume intrinsic, they're free (and, thus, inlining will
-  ; still happen).
+  ; Because these instructions are used only by the @llvm.assume intrinsic,
+  ; they're free and should not be included in the instruction count when
+  ; computing the inline cost.
   %a2 = mul i32 %a1, %a1
-  %a3 = sub i32 %a1, 5
+  %a3 = sub i32 %a1, %a2
   %a4 = udiv i32 %a3, -13
   %a5 = mul i32 %a4, %a4
   %a6 = add i32 %a5, %a5
   %ca = icmp sgt i32 %a6, -7
-  tail call void @llvm.assume(i1 %ca)
+  %r = call i1 @llvm.type.test(i8* %y, metadata !0)
+  %ca2 = icmp eq i1 %ca, %r
+  tail call void @llvm.assume(i1 %ca2)
 
   ret i32 %a1
 }
 
-; @inner() should be inlined for -Oz.
-; CHECK-NOT: call i1 @inner
-define i32 @outer() optsize {
-   %r = call i32 @inner()
+define i32 @outer(i8* %y) optsize {
+   %r = call i32 @inner(i8* %y)
    ret i32 %r
 }
 
 declare void @llvm.assume(i1) nounwind
+declare i1 @llvm.type.test(i8*, metadata) nounwind readnone
 
+!0 = !{i32 0, !"typeid1"}

llvm/test/Transforms/SimplifyCFG/no-md-sink.ll

 
 if.end:
   %t = phi i1 [ %s, %if.else ], [ %r, %if.then ]
   ret i1 %t
 }
 
 ; CHECK-LABEL: test2
 ; CHECK: %[[S:[a-z0-9.]+]] = select i1 %flag, i8* %y, i8* %z
-; CHECK: %[[R:[a-z0-9.]+]] = call i1 @llvm.type.test(i8* %[[S]], metadata !0)
+; CHECK: %[[R:[a-z0-9.]+]] = call i1 @llvm.type.test(i8* %[[S]], metadata ![[MD:[0-9]+]]
 ; CHECK: ret i1 %[[R]]
-
+; CHECK: ![[MD]] = !{i32 0, !"typeid1"}