[DwarfDebug] Improve validThroughout performance (4/4)
Almost NFC (see end).
The backwards scan in validThroughout significantly contributed to compile time
for a pathological case, causing the 'X86 Assembly Printer' pass to account for
roughly 70% of the run time. This patch guards the loop against running
unnecessarily, bringing the pass contribution down to 4%.
Almost NFC: There is a hack in validThroughout which promotes single constant
value DBG_VALUEs in the prologue to be live throughout the function. We're more
likely to hit this code path with this patch applied. Similarly to the parent
patches there is a small coverage change reported in the order of 10s of bytes.
Reviewed By: aprantl
Differential Revision: https://reviews.llvm.org/D86153
diff --git a/llvm/test/DebugInfo/X86/inlined-formal-parameter.ll b/llvm/test/DebugInfo/X86/inlined-formal-parameter.ll
index 00562df..376505f 100644
--- a/llvm/test/DebugInfo/X86/inlined-formal-parameter.ll
+++ b/llvm/test/DebugInfo/X86/inlined-formal-parameter.ll
@@ -19,8 +19,7 @@
; CHECK: DW_TAG_inlined_subroutine
; CHECK-NEXT: DW_AT_abstract_origin {{.*}} "bar"
; CHECK: DW_TAG_formal_parameter
-; CHECK-NEXT: DW_AT_location [DW_FORM_data4] (
-; CHECK-NEXT: [{{.*}}, {{.*}}): DW_OP_consts +0)
+; CHECK-NEXT: DW_AT_const_value [DW_FORM_sdata] (0)
; CHECK-NEXT: DW_AT_abstract_origin {{.*}} "a"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
