From c5060cadf030f6517a1552bf0fc263cb03eb96c4 Mon Sep 17 00:00:00 2001 From: James Greenhalgh Date: Tue, 12 Dec 2017 11:27:54 +0000 Subject: [PATCH] [Patch combine] Don't create vector mode ZERO_EXTEND from subregs The code in simplify set to handle transforming the paradoxical subreg expression: (set FOO (subreg:M (mem:N BAR) 0)) in to: (set FOO (zero_extend:M (mem:N BAR))) Does not consider the case where M is a vector mode, allowing it to construct (for example): (zero_extend:V4SI (mem:SI)) For one, this has the wrong semantics - but fortunately we fail long before then in expand_compound_operation. We need to explicitly reject vector modes from this transformation. gcc/ * combine.c (simplify_set): Do not transform subregs to zero_extends if the destination mode is a vector mode. From-SVN: r255578 --- gcc/ChangeLog | 5 +++++ gcc/combine.c | 4 +++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 8c24c0ec722..ae7adbcf08a 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2017-12-12 James Greenhalgh + + * combine.c (simplify_set): Do not transform subregs to zero_extends + if the destination mode is a vector mode. + 2017-12-12 Jakub Jelinek PR tree-optimization/83359 diff --git a/gcc/combine.c b/gcc/combine.c index f4e94450c09..b6410c3afb0 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -6962,11 +6962,13 @@ simplify_set (rtx x) /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this would require a paradoxical subreg. Replace the subreg with a - zero_extend to avoid the reload that would otherwise be required. */ + zero_extend to avoid the reload that would otherwise be required. + Don't do this for vector modes, as the transformation is incorrect. */ enum rtx_code extend_op; if (paradoxical_subreg_p (src) && MEM_P (SUBREG_REG (src)) + && !VECTOR_MODE_P (GET_MODE (src)) && (extend_op = load_extend_op (GET_MODE (SUBREG_REG (src)))) != UNKNOWN) { SUBST (SET_SRC (x), -- 2.30.2