[ARM/AARCH64] Make test MachineBranchProb.ll more robust and re-enable for ARM/AArch64

[bmakam]

Summary

Make test robust enough to not fail due to CFG changes and re-enable for ARM/AArch64.

[fhahn]

LGTM. Enabling the test on ARM/AArch64 is a definite improvement IMO. Just a nit about the placement of the declare

test/CodeGen/Generic/MachineBranchProb.ll

11 ↗

(On Diff #117851)

Maybe move this declare above the comment, with an extra blank line?

[fhahn]

test/CodeGen/Generic/MachineBranchProb.ll

30 ↗

(On Diff #117851)

Maybe also add a comment that this is here to prevent the SimplifyCFG pass run on AArch64/ARM to mess things up

[bmakam]

I modified the test case per your suggestions before commiting. Thanks for taking a look.

llvm/trunk/test/CodeGen/Generic/MachineBranchProb.ll

 ; RUN: llc < %s -print-machineinstrs=expand-isel-pseudos -o /dev/null 2>&1 | FileCheck %s
 
-; ARM & AArch64 run an extra SimplifyCFG which disrupts this test.
-; UNSUPPORTED: arm,aarch64
-
 ; Hexagon runs passes that renumber the basic blocks, causing this test
 ; to fail.
 ; XFAIL: hexagon
 
 ; Bug: PR31899
 ; XFAIL: avr
 
+declare void @foo()
+
 ; Make sure we have the correct weight attached to each successor.
 define i32 @test2(i32 %x) nounwind uwtable readnone ssp {
 ; CHECK-LABEL: Machine code for function test2:
 entry:
   %conv = sext i32 %x to i64
   switch i64 %conv, label %return [
     i64 0, label %sw.bb
     i64 1, label %sw.bb
     i64 4, label %sw.bb
     i64 5, label %sw.bb1
   ], !prof !0
 ; CHECK: BB#0: derived from LLVM BB %entry
 ; CHECK: Successors according to CFG: BB#2({{[0-9a-fx/= ]+}}75.29%) BB#4({{[0-9a-fx/= ]+}}24.71%)
 ; CHECK: BB#4: derived from LLVM BB %entry
 ; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}47.62%) BB#5({{[0-9a-fx/= ]+}}52.38%)
 ; CHECK: BB#5: derived from LLVM BB %entry
 ; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}36.36%) BB#3({{[0-9a-fx/= ]+}}63.64%)
 
 sw.bb:
+; this call will prevent simplifyCFG from optimizing the block away in ARM/AArch64.
+  tail call void @foo()
   br label %return
 
 sw.bb1:
   br label %return
 
 return:
   %retval.0 = phi i32 [ 5, %sw.bb1 ], [ 1, %sw.bb ], [ 0, %entry ]
   ret i32 %retval.0