https://bugs.llvm.org/show_bug.cgi?id=47801
Bug ID: 47801
Summary: [RegisterScavenger] Spills dead register.
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Common Code Generator Code
Assignee: unassignedb...@nondot.org
Reporter: pauls...@linux.vnet.ibm.com
CC: llvm-bugs@lists.llvm.org
Created attachment 24047
--> https://bugs.llvm.org/attachment.cgi?id=24047&action=edit
reduced testcase
llc -mtriple=s390x-linux-gnu -mcpu=z13 -O3 ./tc_regscav.ll
*** Bad machine code: Using an undefined physical register ***
- function:
- basic block: %bb.0 bb (0x2aa051adc30)
- instruction: STG killed $r6d, $r11d, 168, $noreg :: (store 8 into %stack.26)
- operand 0: killed $r6d
In the test case, register $r6D is killed early in the block by it's only user.
Later in that block, RegisterScavenger decides to use that register for a
virtual register created during Frame Lowering (scavengeFrameVirtualRegs()).
This seems to mean that the RegisterScavenger should actually not need to spill
the register, since it is not live.
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