[llvm] [DebugInfo][RegisterCoalescer] Drop DBG_VALUEs with unsupported register class (PR #143132)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,149 @@
+# Check if DBG_VALUE is set to undef if it doesn't support an updated
+# register class.
+# Input was generated from compiler-rt/lib/builtins/adddf3.c.
+
+# RUN: llc -mtriple i386-apple-macosx10.7.0 -run-pass=register-coalescer %s -o - | FileCheck %s
+
+# CHECK-NOT: DBG_VALUE.*sub_8bit
+# CHECK: DBG_VALUE $noreg
+# CHECK-NOT: DBG_VALUE.*sub_8bit
+
+--- |
+  target datalayout = "e-m:o-p:32:32-p270:32:32-p271:32:32-p272:64:64-i128:128-f64:32:64-f80:128-n8:16:32-S128"
+  target triple = "i386-apple-macosx10.7.0"
+  
+  define i32 @foo(i1 %i) {
+  entry:
+    %shl = or i32 0, 1
+    br i1 %i, label %if.then, label %if.end
+  
+  if.then:                                     ; preds = %entry
+    %cmp = icmp ne i32 %shl, 0
+      #dbg_value(i1 %cmp, !4, !DIExpression(DW_OP_LLVM_convert, 1, DW_ATE_unsigned, DW_OP_LLVM_convert, 8, DW_ATE_unsigned, DW_OP_stack_value), !12)
+    %conv127.i = zext i1 %cmp to i32
+    %or = or i32 %shl, %conv127.i
+    br label %if.end
+  
+  if.end:                                      ; preds = %if.then, %entry
+    %res = phi i32 [ %or, %if.then ], [ 1, %entry ]
+    ret i32 %res
+  }
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arsenm wrote:

Shouldn't need much of anything in the IR section, except maybe some debug metadata. You might be able to get away with DBG_VALUE with missing debug entries 

https://github.com/llvm/llvm-project/pull/143132