MIParser/MIRPrinter: Compute block successors if not explicitely specified

- MIParser: If the successor list is not specified successors will be
  added based on basic block operands in the block and possible
  fallthrough.

- MIRPrinter: Adds a new `simplify-mir` option, with that option set:
  Skip printing of block successor lists in cases where the
  parser is guaranteed to reconstruct it. This means we still print the
  list if some successor cannot be determined (happens for example for
  jump tables), if the successor order changes or branch probabilities
  being unequal.

Differential Revision: https://reviews.llvm.org/D31262

llvm-svn: 302289

4 files changed, 79 insertions, 29 deletions

diff --git a/llvm/test/CodeGen/MIR/Generic/branch-probabilities.ll b/llvm/test/CodeGen/MIR/Generic/branch-probabilities.ll
deleted file mode 100644
index 8d119316b13..00000000000
--- a/llvm/test/CodeGen/MIR/Generic/branch-probabilities.ll
+++ /dev/null
@@ -1,28 +0,0 @@
-; RUN: llc -stop-after machine-sink %s -o %t.mir
-; RUN: FileCheck %s < %t.mir
-; RUN: llc %t.mir -run-pass machine-sink
-; Check that branch probabilities are printed in a format that can then be parsed.
-; This test fails on powerpc because of an undefined physical register use in the MIR.  See PR31062.
-; XFAIL: powerpc
-
-declare void @foo()
-declare void @bar()
-
-define void @test(i1 %c) {
-; CHECK-LABEL: name: test
-entry:
-        br i1 %c, label %then, label %else
-
-then:
-        call void @foo()
-        br label %end
-; CHECK: successors: %{{[a-z0-9\-\.]+}}({{0x[0-9a-f]+}}), %{{[a-z0-9\-\.]+}}({{0x[0-9a-f]+}})
-
-else:
-        call void @bar()
-        br label %end
-; CHECK: successors: %{{[a-z0-9\-\.]+}}({{0x[0-9a-f]+}})
-
-end:
-        ret void
-}
diff --git a/llvm/test/CodeGen/MIR/X86/auto-successor.mir b/llvm/test/CodeGen/MIR/X86/auto-successor.mir
new file mode 100644
index 00000000000..d1b59c35f1e
--- /dev/null
+++ b/llvm/test/CodeGen/MIR/X86/auto-successor.mir
@@ -0,0 +1,61 @@
+# RUN: llc -o - %s -run-pass=none -verify-machineinstrs -simplify-mir | FileCheck %s
+---
+# We shouldn't need any explicit successor lists in these examples
+# CHECK-LABEL: name: func0
+# CHECK: bb.0:
+# CHECK-NOT: successors
+# CHECK: JE_1 %bb.1, implicit undef %eflags
+# CHECK: JMP_1 %bb.3
+# CHECK: bb.1:
+# CHECK-NOT: successors
+# CHECK: bb.2:
+# CHECK-NOT: successors
+# CHECK: JE_1 %bb.1, implicit undef %eflags
+# CHECK: bb.3:
+# CHECK: RETQ undef %eax
+name: func0
+body: |
+  bb.0:
+    JE_1 %bb.1, implicit undef %eflags
+    JMP_1 %bb.3
+
+  bb.1:
+
+  bb.2:
+    JE_1 %bb.1, implicit undef %eflags
+
+  bb.3:
+    JE_1 %bb.4, implicit undef %eflags   ; condjump+fallthrough to same block
+
+  bb.4:
+    RETQ undef %eax
+...
+---
+# Some cases that need explicit successors:
+# CHECK-LABEL: name: func1
+name: func1
+body: |
+  bb.0:
+    ; CHECK: bb.0:
+    ; CHECK: successors: %bb.3, %bb.1
+    successors: %bb.3, %bb.1   ; different order than operands
+    JE_1 %bb.1, implicit undef %eflags
+    JMP_1 %bb.3
+
+  bb.1:
+    ; CHECK: bb.1:
+    ; CHECK: successors: %bb.2, %bb.1
+    successors: %bb.2, %bb.1   ; different order (fallthrough variant)
+    JE_1 %bb.1, implicit undef %eflags
+
+  bb.2:
+    ; CHECK: bb.2:
+    ; CHECK: successors: %bb.1(0x60000000), %bb.3(0x20000000)
+    successors: %bb.1(3), %bb.3(1)  ; branch probabilities not normalized
+    JE_1 %bb.1, implicit undef %eflags
+
+  bb.3:
+    ; CHECK: bb.3:
+    ; CHECK: RETQ undef %eax
+    RETQ undef %eax
+...
diff --git a/llvm/test/CodeGen/MIR/X86/branch-probabilities.mir b/llvm/test/CodeGen/MIR/X86/branch-probabilities.mir
new file mode 100644
index 00000000000..4aacd2d5cef
--- /dev/null
+++ b/llvm/test/CodeGen/MIR/X86/branch-probabilities.mir
@@ -0,0 +1,18 @@
+# RUN: llc -o - %s -mtriple=x86_64-- -run-pass=none | FileCheck %s
+---
+# Check that branch probabilities are printed correctly as hex numbers.
+# CHECK-LABEL: name: test
+# CHECK: bb.0:
+# CHECK-NEXT: successors: %bb.1(0x66666666), %bb.2(0x1999999a)
+name: test
+body: |
+  bb.0:
+    successors: %bb.1(4), %bb.2(1)
+    JE_1 %bb.2, implicit undef %eflags
+
+  bb.1:
+    NOOP
+
+  bb.2:
+    RETQ undef %eax
+...
diff --git a/llvm/test/CodeGen/MIR/X86/successor-basic-blocks.mir b/llvm/test/CodeGen/MIR/X86/successor-basic-blocks.mir
index 395272bb23c..ffeb04af9e4 100644
--- a/llvm/test/CodeGen/MIR/X86/successor-basic-blocks.mir
+++ b/llvm/test/CodeGen/MIR/X86/successor-basic-blocks.mir
@@ -32,7 +32,6 @@
 name:            foo
 body: |
   ; CHECK-LABEL: bb.0.entry:
-  ; CHECK:         successors: %bb.1.less(0x40000000), %bb.2.exit(0x40000000)
   ; CHECK-LABEL: bb.1.less:
   bb.0.entry:
     successors: %bb.1.less, %bb.2.exit