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| -rw-r--r-- | lib/CodeGen/README.txt | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/CodeGen/README.txt b/lib/CodeGen/README.txt new file mode 100644 index 0000000000..3f295126fb --- /dev/null +++ b/lib/CodeGen/README.txt @@ -0,0 +1,27 @@ +Common register allocation / spilling problem: + + mul lr, r4, lr + str lr, [sp, #+52] + ldr lr, [r1, #+32] + sxth r3, r3 + ldr r4, [sp, #+52] + mla r4, r3, lr, r4 + +can be: + + mul lr, r4, lr + mov r4, lr + str lr, [sp, #+52] + ldr lr, [r1, #+32] + sxth r3, r3 + mla r4, r3, lr, r4 + +and then "merge" mul and mov: + + mul r4, r4, lr + str lr, [sp, #+52] + ldr lr, [r1, #+32] + sxth r3, r3 + mla r4, r3, lr, r4 + +It also increase the likelyhood the store may become dead. |